From 0a949aaff26b9680362bf1a8c580fabadef848aa Mon Sep 17 00:00:00 2001
From: Cian Johnston <cian@coder.com>
Date: Mon, 13 Jun 2022 22:09:36 +0100
Subject: [PATCH] cli: streamline autostart ux (#2251)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

This commit adds the following changes:

- autostart enable|disable => autostart set|unset
- autostart enable now accepts a more natual schedule format: <time> <days-of-week> <location>
- autostart show now shows configured timezone
- 🎉 automatic timezone detection across mac, windows, linux 🎉

Fixes #1647
---
 cli/autostart.go                           | 157 ++++++++++++++++-----
 cli/autostart_internal_test.go             | 119 ++++++++++++++++
 cli/autostart_test.go                      | 104 +++++---------
 coderd/autobuild/schedule/schedule.go      |  30 +++-
 coderd/autobuild/schedule/schedule_test.go | 105 ++++++++------
 coderd/util/tz/tz.go                       |  30 ++++
 coderd/util/tz/tz_darwin.go                |  50 +++++++
 coderd/util/tz/tz_linux.go                 |  44 ++++++
 coderd/util/tz/tz_test.go                  |  40 ++++++
 coderd/util/tz/tz_windows.go               |  55 ++++++++
 10 files changed, 585 insertions(+), 149 deletions(-)
 create mode 100644 cli/autostart_internal_test.go
 create mode 100644 coderd/util/tz/tz.go
 create mode 100644 coderd/util/tz/tz_darwin.go
 create mode 100644 coderd/util/tz/tz_linux.go
 create mode 100644 coderd/util/tz/tz_test.go
 create mode 100644 coderd/util/tz/tz_windows.go

diff --git a/cli/autostart.go b/cli/autostart.go
index 2735b5a42d..dd413a0498 100644
--- a/cli/autostart.go
+++ b/cli/autostart.go
@@ -2,32 +2,41 @@ package cli
 
 import (
 	"fmt"
-	"os"
+	"strings"
 	"time"
 
 	"github.com/spf13/cobra"
+	"golang.org/x/xerrors"
 
 	"github.com/coder/coder/coderd/autobuild/schedule"
+	"github.com/coder/coder/coderd/util/ptr"
+	"github.com/coder/coder/coderd/util/tz"
 	"github.com/coder/coder/codersdk"
 )
 
 const autostartDescriptionLong = `To have your workspace build automatically at a regular time you can enable autostart.
-When enabling autostart, provide the minute, hour, and day(s) of week.
-The default schedule is at 09:00 in your local timezone (TZ env, UTC by default).
+When enabling autostart, enter a schedule in the format: <start-time> [day-of-week] [location].
+  * Start-time (required) is accepted either in 12-hour (hh:mm{am|pm}) format, or 24-hour format hh:mm.
+  * Day-of-week (optional) allows specifying in the cron format, e.g. 1,3,5 or Mon-Fri.
+    Aliases such as @daily are not supported.
+    Default: * (every day)
+  * Location (optional) must be a valid location in the IANA timezone database.
+    If omitted, we will fall back to either the TZ environment variable or /etc/localtime.
+    You can check your corresponding location by visiting https://ipinfo.io - it shows in the demo widget on the right.
 `
 
 func autostart() *cobra.Command {
 	autostartCmd := &cobra.Command{
 		Annotations: workspaceCommand,
-		Use:         "autostart enable <workspace>",
+		Use:         "autostart set <workspace> <start-time> [day-of-week] [location]",
 		Short:       "schedule a workspace to automatically start at a regular time",
 		Long:        autostartDescriptionLong,
-		Example:     "coder autostart enable my-workspace --minute 30 --hour 9 --days 1-5 --tz Europe/Dublin",
+		Example:     "coder autostart set my-workspace 9:30AM Mon-Fri Europe/Dublin",
 	}
 
 	autostartCmd.AddCommand(autostartShow())
-	autostartCmd.AddCommand(autostartEnable())
-	autostartCmd.AddCommand(autostartDisable())
+	autostartCmd.AddCommand(autostartSet())
+	autostartCmd.AddCommand(autostartUnset())
 
 	return autostartCmd
 }
@@ -60,13 +69,12 @@ func autostartShow() *cobra.Command {
 			}
 
 			next := validSchedule.Next(time.Now())
-			loc, _ := time.LoadLocation(validSchedule.Timezone())
 
 			_, _ = fmt.Fprintf(cmd.OutOrStdout(),
 				"schedule: %s\ntimezone: %s\nnext:     %s\n",
 				validSchedule.Cron(),
-				validSchedule.Timezone(),
-				next.In(loc),
+				validSchedule.Location(),
+				next.In(validSchedule.Location()),
 			)
 
 			return nil
@@ -75,23 +83,17 @@ func autostartShow() *cobra.Command {
 	return cmd
 }
 
-func autostartEnable() *cobra.Command {
-	// yes some of these are technically numbers but the cron library will do that work
-	var autostartMinute string
-	var autostartHour string
-	var autostartDayOfWeek string
-	var autostartTimezone string
+func autostartSet() *cobra.Command {
 	cmd := &cobra.Command{
-		Use:  "enable <workspace_name> <schedule>",
-		Args: cobra.ExactArgs(1),
+		Use:  "set <workspace_name> <start-time> [day-of-week] [location]",
+		Args: cobra.RangeArgs(2, 4),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			client, err := createClient(cmd)
 			if err != nil {
 				return err
 			}
 
-			spec := fmt.Sprintf("CRON_TZ=%s %s %s * * %s", autostartTimezone, autostartMinute, autostartHour, autostartDayOfWeek)
-			validSchedule, err := schedule.Weekly(spec)
+			sched, err := parseCLISchedule(args[1:]...)
 			if err != nil {
 				return err
 			}
@@ -102,32 +104,30 @@ func autostartEnable() *cobra.Command {
 			}
 
 			err = client.UpdateWorkspaceAutostart(cmd.Context(), workspace.ID, codersdk.UpdateWorkspaceAutostartRequest{
-				Schedule: &spec,
+				Schedule: ptr.Ref(sched.String()),
 			})
 			if err != nil {
 				return err
 			}
 
-			_, _ = fmt.Fprintf(cmd.OutOrStdout(), "\nThe %s workspace will automatically start at %s.\n\n", workspace.Name, validSchedule.Next(time.Now()))
-
+			schedNext := sched.Next(time.Now())
+			_, _ = fmt.Fprintf(cmd.OutOrStdout(),
+				"%s will automatically start at %s %s (%s)\n",
+				workspace.Name,
+				schedNext.In(sched.Location()).Format(time.Kitchen),
+				sched.DaysOfWeek(),
+				sched.Location().String(),
+			)
 			return nil
 		},
 	}
 
-	cmd.Flags().StringVar(&autostartMinute, "minute", "0", "autostart minute")
-	cmd.Flags().StringVar(&autostartHour, "hour", "9", "autostart hour")
-	cmd.Flags().StringVar(&autostartDayOfWeek, "days", "1-5", "autostart day(s) of week")
-	tzEnv := os.Getenv("TZ")
-	if tzEnv == "" {
-		tzEnv = "UTC"
-	}
-	cmd.Flags().StringVar(&autostartTimezone, "tz", tzEnv, "autostart timezone")
 	return cmd
 }
 
-func autostartDisable() *cobra.Command {
+func autostartUnset() *cobra.Command {
 	return &cobra.Command{
-		Use:  "disable <workspace_name>",
+		Use:  "unset <workspace_name>",
 		Args: cobra.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
 			client, err := createClient(cmd)
@@ -147,9 +147,98 @@ func autostartDisable() *cobra.Command {
 				return err
 			}
 
-			_, _ = fmt.Fprintf(cmd.OutOrStdout(), "\nThe %s workspace will no longer automatically start.\n\n", workspace.Name)
+			_, _ = fmt.Fprintf(cmd.OutOrStdout(), "%s will no longer automatically start.\n", workspace.Name)
 
 			return nil
 		},
 	}
 }
+
+var errInvalidScheduleFormat = xerrors.New("Schedule must be in the format Mon-Fri 09:00AM America/Chicago")
+var errInvalidTimeFormat = xerrors.New("Start time must be in the format hh:mm[am|pm] or HH:MM")
+var errUnsupportedTimezone = xerrors.New("The location you provided looks like a timezone. Check https://ipinfo.io for your location.")
+
+// parseCLISchedule parses a schedule in the format HH:MM{AM|PM} [DOW] [LOCATION]
+func parseCLISchedule(parts ...string) (*schedule.Schedule, error) {
+	// If the user was careful and quoted the schedule, un-quote it.
+	// In the case that only time was specified, this will be a no-op.
+	if len(parts) == 1 {
+		parts = strings.Fields(parts[0])
+	}
+	var loc *time.Location
+	dayOfWeek := "*"
+	t, err := parseTime(parts[0])
+	if err != nil {
+		return nil, err
+	}
+	hour, minute := t.Hour(), t.Minute()
+
+	// Any additional parts get ignored.
+	switch len(parts) {
+	case 3:
+		dayOfWeek = parts[1]
+		loc, err = time.LoadLocation(parts[2])
+		if err != nil {
+			_, err = time.Parse("MST", parts[2])
+			if err == nil {
+				return nil, errUnsupportedTimezone
+			}
+			return nil, xerrors.Errorf("Invalid timezone %q specified: a valid IANA timezone is required", parts[2])
+		}
+	case 2:
+		// Did they provide day-of-week or location?
+		if maybeLoc, err := time.LoadLocation(parts[1]); err != nil {
+			// Assume day-of-week.
+			dayOfWeek = parts[1]
+		} else {
+			loc = maybeLoc
+		}
+	case 1: // already handled
+	default:
+		return nil, errInvalidScheduleFormat
+	}
+
+	// If location was not specified, attempt to automatically determine it as a last resort.
+	if loc == nil {
+		loc, err = tz.TimezoneIANA()
+		if err != nil {
+			return nil, xerrors.Errorf("Could not automatically determine your timezone")
+		}
+	}
+
+	sched, err := schedule.Weekly(fmt.Sprintf(
+		"CRON_TZ=%s %d %d * * %s",
+		loc.String(),
+		minute,
+		hour,
+		dayOfWeek,
+	))
+	if err != nil {
+		// This will either be an invalid dayOfWeek or an invalid timezone.
+		return nil, xerrors.Errorf("Invalid schedule: %w", err)
+	}
+
+	return sched, nil
+}
+
+func parseTime(s string) (time.Time, error) {
+	// Try a number of possible layouts.
+	for _, layout := range []string{
+		time.Kitchen, // 03:04PM
+		"03:04pm",
+		"3:04PM",
+		"3:04pm",
+		"15:04",
+		"1504",
+		"03PM",
+		"03pm",
+		"3PM",
+		"3pm",
+	} {
+		t, err := time.Parse(layout, s)
+		if err == nil {
+			return t, nil
+		}
+	}
+	return time.Time{}, errInvalidTimeFormat
+}
diff --git a/cli/autostart_internal_test.go b/cli/autostart_internal_test.go
new file mode 100644
index 0000000000..cdbbb9ca6c
--- /dev/null
+++ b/cli/autostart_internal_test.go
@@ -0,0 +1,119 @@
+package cli
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+//nolint:paralleltest // t.Setenv
+func TestParseCLISchedule(t *testing.T) {
+	for _, testCase := range []struct {
+		name             string
+		input            []string
+		expectedSchedule string
+		expectedError    string
+		tzEnv            string
+	}{
+		{
+			name:             "TimeAndDayOfWeekAndLocation",
+			input:            []string{"09:00AM", "Sun-Sat", "America/Chicago"},
+			expectedSchedule: "CRON_TZ=America/Chicago 0 9 * * Sun-Sat",
+			tzEnv:            "UTC",
+		},
+		{
+			name:             "TimeOfDay24HourAndDayOfWeekAndLocation",
+			input:            []string{"09:00", "Sun-Sat", "America/Chicago"},
+			expectedSchedule: "CRON_TZ=America/Chicago 0 9 * * Sun-Sat",
+			tzEnv:            "UTC",
+		},
+		{
+			name:             "TimeOfDay24HourAndDayOfWeekAndLocationButItsAllQuoted",
+			input:            []string{"09:00 Sun-Sat America/Chicago"},
+			expectedSchedule: "CRON_TZ=America/Chicago 0 9 * * Sun-Sat",
+			tzEnv:            "UTC",
+		},
+		{
+			name:             "TimeOfDayOnly",
+			input:            []string{"09:00AM"},
+			expectedSchedule: "CRON_TZ=America/Chicago 0 9 * * *",
+			tzEnv:            "America/Chicago",
+		},
+		{
+			name:             "Time24Military",
+			input:            []string{"0900"},
+			expectedSchedule: "CRON_TZ=America/Chicago 0 9 * * *",
+			tzEnv:            "America/Chicago",
+		},
+		{
+			name:             "DayOfWeekAndTime",
+			input:            []string{"09:00AM", "Sun-Sat"},
+			expectedSchedule: "CRON_TZ=America/Chicago 0 9 * * Sun-Sat",
+			tzEnv:            "America/Chicago",
+		},
+		{
+			name:             "TimeAndLocation",
+			input:            []string{"09:00AM", "America/Chicago"},
+			expectedSchedule: "CRON_TZ=America/Chicago 0 9 * * *",
+			tzEnv:            "UTC",
+		},
+		{
+			name:             "LazyTime",
+			input:            []string{"9am", "America/Chicago"},
+			expectedSchedule: "CRON_TZ=America/Chicago 0 9 * * *",
+			tzEnv:            "UTC",
+		},
+		{
+			name:             "ZeroPrefixedLazyTime",
+			input:            []string{"09am", "America/Chicago"},
+			expectedSchedule: "CRON_TZ=America/Chicago 0 9 * * *",
+			tzEnv:            "UTC",
+		},
+		{
+			name:          "InvalidTime",
+			input:         []string{"nine"},
+			expectedError: errInvalidTimeFormat.Error(),
+		},
+		{
+			name:          "DayOfWeekAndInvalidTime",
+			input:         []string{"nine", "Sun-Sat"},
+			expectedError: errInvalidTimeFormat.Error(),
+		},
+		{
+			name:          "InvalidTimeAndLocation",
+			input:         []string{"nine", "America/Chicago"},
+			expectedError: errInvalidTimeFormat.Error(),
+		},
+		{
+			name:          "DayOfWeekAndInvalidTimeAndLocation",
+			input:         []string{"nine", "Sun-Sat", "America/Chicago"},
+			expectedError: errInvalidTimeFormat.Error(),
+		},
+		{
+			name:          "TimezoneProvidedInsteadOfLocation",
+			input:         []string{"09:00AM", "Sun-Sat", "CST"},
+			expectedError: errUnsupportedTimezone.Error(),
+		},
+		{
+			name:          "WhoKnows",
+			input:         []string{"Time", "is", "a", "human", "construct"},
+			expectedError: errInvalidTimeFormat.Error(),
+		},
+	} {
+		testCase := testCase
+		//nolint:paralleltest // t.Setenv
+		t.Run(testCase.name, func(t *testing.T) {
+			t.Setenv("TZ", testCase.tzEnv)
+			actualSchedule, actualError := parseCLISchedule(testCase.input...)
+			if testCase.expectedError != "" {
+				assert.Nil(t, actualSchedule)
+				assert.ErrorContains(t, actualError, testCase.expectedError)
+				return
+			}
+			assert.NoError(t, actualError)
+			if assert.NotEmpty(t, actualSchedule) {
+				assert.Equal(t, testCase.expectedSchedule, actualSchedule.String())
+			}
+		})
+	}
+}
diff --git a/cli/autostart_test.go b/cli/autostart_test.go
index fd295fa8e4..5fae0777e5 100644
--- a/cli/autostart_test.go
+++ b/cli/autostart_test.go
@@ -4,9 +4,7 @@ import (
 	"bytes"
 	"context"
 	"fmt"
-	"os"
 	"testing"
-	"time"
 
 	"github.com/stretchr/testify/require"
 
@@ -50,7 +48,7 @@ func TestAutostart(t *testing.T) {
 		require.Contains(t, stdoutBuf.String(), "schedule: 30 17 * * 1-5")
 	})
 
-	t.Run("EnableDisableOK", func(t *testing.T) {
+	t.Run("setunsetOK", func(t *testing.T) {
 		t.Parallel()
 
 		var (
@@ -62,8 +60,8 @@ func TestAutostart(t *testing.T) {
 			project   = coderdtest.CreateTemplate(t, client, user.OrganizationID, version.ID)
 			workspace = coderdtest.CreateWorkspace(t, client, user.OrganizationID, project.ID)
 			tz        = "Europe/Dublin"
-			cmdArgs   = []string{"autostart", "enable", workspace.Name, "--minute", "30", "--hour", "9", "--days", "1-5", "--tz", tz}
-			sched     = "CRON_TZ=Europe/Dublin 30 9 * * 1-5"
+			cmdArgs   = []string{"autostart", "set", workspace.Name, "9:30AM", "Mon-Fri", tz}
+			sched     = "CRON_TZ=Europe/Dublin 30 9 * * Mon-Fri"
 			stdoutBuf = &bytes.Buffer{}
 		)
 
@@ -73,15 +71,15 @@ func TestAutostart(t *testing.T) {
 
 		err := cmd.Execute()
 		require.NoError(t, err, "unexpected error")
-		require.Contains(t, stdoutBuf.String(), "will automatically start at", "unexpected output")
+		require.Contains(t, stdoutBuf.String(), "will automatically start at 9:30AM Mon-Fri (Europe/Dublin)", "unexpected output")
 
 		// Ensure autostart schedule updated
 		updated, err := client.Workspace(ctx, workspace.ID)
 		require.NoError(t, err, "fetch updated workspace")
 		require.Equal(t, sched, *updated.AutostartSchedule, "expected autostart schedule to be set")
 
-		// Disable schedule
-		cmd, root = clitest.New(t, "autostart", "disable", workspace.Name)
+		// unset schedule
+		cmd, root = clitest.New(t, "autostart", "unset", workspace.Name)
 		clitest.SetupConfig(t, client, root)
 		cmd.SetOut(stdoutBuf)
 
@@ -95,7 +93,7 @@ func TestAutostart(t *testing.T) {
 		require.Nil(t, updated.AutostartSchedule, "expected autostart schedule to not be set")
 	})
 
-	t.Run("Enable_NotFound", func(t *testing.T) {
+	t.Run("set_NotFound", func(t *testing.T) {
 		t.Parallel()
 
 		var (
@@ -105,14 +103,14 @@ func TestAutostart(t *testing.T) {
 			_       = coderdtest.AwaitTemplateVersionJob(t, client, version.ID)
 		)
 
-		cmd, root := clitest.New(t, "autostart", "enable", "doesnotexist")
+		cmd, root := clitest.New(t, "autostart", "set", "doesnotexist", "09:30AM")
 		clitest.SetupConfig(t, client, root)
 
 		err := cmd.Execute()
 		require.ErrorContains(t, err, "status code 403: Forbidden", "unexpected error")
 	})
 
-	t.Run("Disable_NotFound", func(t *testing.T) {
+	t.Run("unset_NotFound", func(t *testing.T) {
 		t.Parallel()
 
 		var (
@@ -122,63 +120,39 @@ func TestAutostart(t *testing.T) {
 			_       = coderdtest.AwaitTemplateVersionJob(t, client, version.ID)
 		)
 
-		cmd, root := clitest.New(t, "autostart", "disable", "doesnotexist")
+		cmd, root := clitest.New(t, "autostart", "unset", "doesnotexist")
 		clitest.SetupConfig(t, client, root)
 
 		err := cmd.Execute()
 		require.ErrorContains(t, err, "status code 403: Forbidden", "unexpected error")
 	})
-
-	t.Run("Enable_DefaultSchedule", func(t *testing.T) {
-		t.Parallel()
-
-		var (
-			ctx       = context.Background()
-			client    = coderdtest.New(t, &coderdtest.Options{IncludeProvisionerD: true})
-			user      = coderdtest.CreateFirstUser(t, client)
-			version   = coderdtest.CreateTemplateVersion(t, client, user.OrganizationID, nil)
-			_         = coderdtest.AwaitTemplateVersionJob(t, client, version.ID)
-			project   = coderdtest.CreateTemplate(t, client, user.OrganizationID, version.ID)
-			workspace = coderdtest.CreateWorkspace(t, client, user.OrganizationID, project.ID)
-		)
-
-		// check current TZ env var
-		currTz := os.Getenv("TZ")
-		if currTz == "" {
-			currTz = "UTC"
-		}
-		expectedSchedule := fmt.Sprintf("CRON_TZ=%s 0 9 * * 1-5", currTz)
-		cmd, root := clitest.New(t, "autostart", "enable", workspace.Name)
-		clitest.SetupConfig(t, client, root)
-
-		err := cmd.Execute()
-		require.NoError(t, err, "unexpected error")
-
-		// Ensure nothing happened
-		updated, err := client.Workspace(ctx, workspace.ID)
-		require.NoError(t, err, "fetch updated workspace")
-		require.Equal(t, expectedSchedule, *updated.AutostartSchedule, "expected default autostart schedule")
-	})
-
-	t.Run("BelowTemplateConstraint", func(t *testing.T) {
-		t.Parallel()
-
-		var (
-			client  = coderdtest.New(t, &coderdtest.Options{IncludeProvisionerD: true})
-			user    = coderdtest.CreateFirstUser(t, client)
-			version = coderdtest.CreateTemplateVersion(t, client, user.OrganizationID, nil)
-			_       = coderdtest.AwaitTemplateVersionJob(t, client, version.ID)
-			project = coderdtest.CreateTemplate(t, client, user.OrganizationID, version.ID, func(ctr *codersdk.CreateTemplateRequest) {
-				ctr.MinAutostartIntervalMillis = ptr.Ref(time.Hour.Milliseconds())
-			})
-			workspace = coderdtest.CreateWorkspace(t, client, user.OrganizationID, project.ID)
-			cmdArgs   = []string{"autostart", "enable", workspace.Name, "--minute", "*", "--hour", "*"}
-		)
-
-		cmd, root := clitest.New(t, cmdArgs...)
-		clitest.SetupConfig(t, client, root)
-
-		err := cmd.Execute()
-		require.ErrorContains(t, err, "schedule: Minimum autostart interval 1m0s below template minimum 1h0m0s")
-	})
+}
+
+//nolint:paralleltest // t.Setenv
+func TestAutostartSetDefaultSchedule(t *testing.T) {
+	t.Setenv("TZ", "UTC")
+	var (
+		ctx       = context.Background()
+		client    = coderdtest.New(t, &coderdtest.Options{IncludeProvisionerD: true})
+		user      = coderdtest.CreateFirstUser(t, client)
+		version   = coderdtest.CreateTemplateVersion(t, client, user.OrganizationID, nil)
+		_         = coderdtest.AwaitTemplateVersionJob(t, client, version.ID)
+		project   = coderdtest.CreateTemplate(t, client, user.OrganizationID, version.ID)
+		workspace = coderdtest.CreateWorkspace(t, client, user.OrganizationID, project.ID)
+		stdoutBuf = &bytes.Buffer{}
+	)
+
+	expectedSchedule := fmt.Sprintf("CRON_TZ=%s 30 9 * * *", "UTC")
+	cmd, root := clitest.New(t, "autostart", "set", workspace.Name, "9:30AM")
+	clitest.SetupConfig(t, client, root)
+	cmd.SetOutput(stdoutBuf)
+
+	err := cmd.Execute()
+	require.NoError(t, err, "unexpected error")
+
+	// Ensure nothing happened
+	updated, err := client.Workspace(ctx, workspace.ID)
+	require.NoError(t, err, "fetch updated workspace")
+	require.Equal(t, expectedSchedule, *updated.AutostartSchedule, "expected default autostart schedule")
+	require.Contains(t, stdoutBuf.String(), "will automatically start at 9:30AM daily (UTC)")
 }
diff --git a/coderd/autobuild/schedule/schedule.go b/coderd/autobuild/schedule/schedule.go
index de729982c7..a687593478 100644
--- a/coderd/autobuild/schedule/schedule.go
+++ b/coderd/autobuild/schedule/schedule.go
@@ -3,6 +3,7 @@
 package schedule
 
 import (
+	"fmt"
 	"strings"
 	"time"
 
@@ -74,7 +75,8 @@ func Weekly(raw string) (*Schedule, error) {
 }
 
 // Schedule represents a cron schedule.
-// It's essentially a thin wrapper for robfig/cron/v3 that implements Stringer.
+// It's essentially a wrapper for robfig/cron/v3 that has additional
+// convenience methods.
 type Schedule struct {
 	sched *cron.SpecSchedule
 	// XXX: there isn't any nice way for robfig/cron to serialize
@@ -92,9 +94,9 @@ func (s Schedule) String() string {
 	return sb.String()
 }
 
-// Timezone returns the timezone for the schedule.
-func (s Schedule) Timezone() string {
-	return s.sched.Location.String()
+// Location returns the IANA location for the schedule.
+func (s Schedule) Location() *time.Location {
+	return s.sched.Location
 }
 
 // Cron returns the cron spec for the schedule with the leading CRON_TZ
@@ -137,6 +139,26 @@ func (s Schedule) Min() time.Duration {
 	return durMin
 }
 
+// DaysOfWeek returns a humanized form of the day-of-week field.
+func (s Schedule) DaysOfWeek() string {
+	dow := strings.Fields(s.cronStr)[4]
+	if dow == "*" {
+		return "daily"
+	}
+	for _, weekday := range []time.Weekday{
+		time.Sunday,
+		time.Monday,
+		time.Tuesday,
+		time.Wednesday,
+		time.Thursday,
+		time.Friday,
+		time.Saturday,
+	} {
+		dow = strings.Replace(dow, fmt.Sprintf("%d", weekday), weekday.String()[:3], 1)
+	}
+	return dow
+}
+
 // validateWeeklySpec ensures that the day-of-month and month options of
 // spec are both set to *
 func validateWeeklySpec(spec string) error {
diff --git a/coderd/autobuild/schedule/schedule_test.go b/coderd/autobuild/schedule/schedule_test.go
index c666b82f08..fee40232e9 100644
--- a/coderd/autobuild/schedule/schedule_test.go
+++ b/coderd/autobuild/schedule/schedule_test.go
@@ -12,59 +12,64 @@ import (
 func Test_Weekly(t *testing.T) {
 	t.Parallel()
 	testCases := []struct {
-		name           string
-		spec           string
-		at             time.Time
-		expectedNext   time.Time
-		expectedMin    time.Duration
-		expectedError  string
-		expectedCron   string
-		expectedTz     string
-		expectedString string
+		name               string
+		spec               string
+		at                 time.Time
+		expectedNext       time.Time
+		expectedMin        time.Duration
+		expectedDaysOfWeek string
+		expectedError      string
+		expectedCron       string
+		expectedLocation   *time.Location
+		expectedString     string
 	}{
 		{
-			name:           "with timezone",
-			spec:           "CRON_TZ=US/Central 30 9 * * 1-5",
-			at:             time.Date(2022, 4, 1, 14, 29, 0, 0, time.UTC),
-			expectedNext:   time.Date(2022, 4, 1, 14, 30, 0, 0, time.UTC),
-			expectedMin:    24 * time.Hour,
-			expectedError:  "",
-			expectedCron:   "30 9 * * 1-5",
-			expectedTz:     "US/Central",
-			expectedString: "CRON_TZ=US/Central 30 9 * * 1-5",
+			name:               "with timezone",
+			spec:               "CRON_TZ=US/Central 30 9 * * 1-5",
+			at:                 time.Date(2022, 4, 1, 14, 29, 0, 0, time.UTC),
+			expectedNext:       time.Date(2022, 4, 1, 14, 30, 0, 0, time.UTC),
+			expectedMin:        24 * time.Hour,
+			expectedDaysOfWeek: "Mon-Fri",
+			expectedError:      "",
+			expectedCron:       "30 9 * * 1-5",
+			expectedLocation:   mustLocation(t, "US/Central"),
+			expectedString:     "CRON_TZ=US/Central 30 9 * * 1-5",
 		},
 		{
-			name:           "without timezone",
-			spec:           "30 9 * * 1-5",
-			at:             time.Date(2022, 4, 1, 9, 29, 0, 0, time.UTC),
-			expectedNext:   time.Date(2022, 4, 1, 9, 30, 0, 0, time.UTC),
-			expectedMin:    24 * time.Hour,
-			expectedError:  "",
-			expectedCron:   "30 9 * * 1-5",
-			expectedTz:     "UTC",
-			expectedString: "CRON_TZ=UTC 30 9 * * 1-5",
+			name:               "without timezone",
+			spec:               "30 9 * * 1-5",
+			at:                 time.Date(2022, 4, 1, 9, 29, 0, 0, time.UTC),
+			expectedNext:       time.Date(2022, 4, 1, 9, 30, 0, 0, time.UTC),
+			expectedMin:        24 * time.Hour,
+			expectedDaysOfWeek: "Mon-Fri",
+			expectedError:      "",
+			expectedCron:       "30 9 * * 1-5",
+			expectedLocation:   time.UTC,
+			expectedString:     "CRON_TZ=UTC 30 9 * * 1-5",
 		},
 		{
-			name:           "convoluted with timezone",
-			spec:           "CRON_TZ=US/Central */5 12-18 * * 1,3,6",
-			at:             time.Date(2022, 4, 1, 14, 29, 0, 0, time.UTC),
-			expectedNext:   time.Date(2022, 4, 2, 17, 0, 0, 0, time.UTC), // Apr 1 was a Friday in 2022
-			expectedMin:    5 * time.Minute,
-			expectedError:  "",
-			expectedCron:   "*/5 12-18 * * 1,3,6",
-			expectedTz:     "US/Central",
-			expectedString: "CRON_TZ=US/Central */5 12-18 * * 1,3,6",
+			name:               "convoluted with timezone",
+			spec:               "CRON_TZ=US/Central */5 12-18 * * 1,3,6",
+			at:                 time.Date(2022, 4, 1, 14, 29, 0, 0, time.UTC),
+			expectedNext:       time.Date(2022, 4, 2, 17, 0, 0, 0, time.UTC), // Apr 1 was a Friday in 2022
+			expectedMin:        5 * time.Minute,
+			expectedDaysOfWeek: "Mon,Wed,Sat",
+			expectedError:      "",
+			expectedCron:       "*/5 12-18 * * 1,3,6",
+			expectedLocation:   mustLocation(t, "US/Central"),
+			expectedString:     "CRON_TZ=US/Central */5 12-18 * * 1,3,6",
 		},
 		{
-			name:           "another convoluted example",
-			spec:           "CRON_TZ=US/Central 10,20,40-50 * * * *",
-			at:             time.Date(2022, 4, 1, 14, 29, 0, 0, time.UTC),
-			expectedNext:   time.Date(2022, 4, 1, 14, 40, 0, 0, time.UTC),
-			expectedMin:    time.Minute,
-			expectedError:  "",
-			expectedCron:   "10,20,40-50 * * * *",
-			expectedTz:     "US/Central",
-			expectedString: "CRON_TZ=US/Central 10,20,40-50 * * * *",
+			name:               "another convoluted example",
+			spec:               "CRON_TZ=US/Central 10,20,40-50 * * * *",
+			at:                 time.Date(2022, 4, 1, 14, 29, 0, 0, time.UTC),
+			expectedNext:       time.Date(2022, 4, 1, 14, 40, 0, 0, time.UTC),
+			expectedMin:        time.Minute,
+			expectedDaysOfWeek: "daily",
+			expectedError:      "",
+			expectedCron:       "10,20,40-50 * * * *",
+			expectedLocation:   mustLocation(t, "US/Central"),
+			expectedString:     "CRON_TZ=US/Central 10,20,40-50 * * * *",
 		},
 		{
 			name:          "time.Local will bite you",
@@ -127,9 +132,10 @@ func Test_Weekly(t *testing.T) {
 				require.NoError(t, err)
 				require.Equal(t, testCase.expectedNext, nextTime)
 				require.Equal(t, testCase.expectedCron, actual.Cron())
-				require.Equal(t, testCase.expectedTz, actual.Timezone())
+				require.Equal(t, testCase.expectedLocation, actual.Location())
 				require.Equal(t, testCase.expectedString, actual.String())
 				require.Equal(t, testCase.expectedMin, actual.Min())
+				require.Equal(t, testCase.expectedDaysOfWeek, actual.DaysOfWeek())
 			} else {
 				require.EqualError(t, err, testCase.expectedError)
 				require.Nil(t, actual)
@@ -137,3 +143,10 @@ func Test_Weekly(t *testing.T) {
 		})
 	}
 }
+
+func mustLocation(t *testing.T, s string) *time.Location {
+	t.Helper()
+	loc, err := time.LoadLocation(s)
+	require.NoError(t, err)
+	return loc
+}
diff --git a/coderd/util/tz/tz.go b/coderd/util/tz/tz.go
new file mode 100644
index 0000000000..09687a9993
--- /dev/null
+++ b/coderd/util/tz/tz.go
@@ -0,0 +1,30 @@
+// Package tz includes utilities for cross-platform timezone/location detection.
+package tz
+
+import (
+	"os"
+	"time"
+
+	"golang.org/x/xerrors"
+)
+
+var errNoEnvSet = xerrors.New("no env set")
+
+func locationFromEnv() (*time.Location, error) {
+	tzEnv, found := os.LookupEnv("TZ")
+	if !found {
+		return nil, errNoEnvSet
+	}
+
+	// TZ set but empty means UTC.
+	if tzEnv == "" {
+		return time.UTC, nil
+	}
+
+	loc, err := time.LoadLocation(tzEnv)
+	if err != nil {
+		return nil, xerrors.Errorf("load location from TZ env: %w", err)
+	}
+
+	return loc, nil
+}
diff --git a/coderd/util/tz/tz_darwin.go b/coderd/util/tz/tz_darwin.go
new file mode 100644
index 0000000000..88ed56f785
--- /dev/null
+++ b/coderd/util/tz/tz_darwin.go
@@ -0,0 +1,50 @@
+//go:build darwin
+
+package tz
+
+import (
+	"path/filepath"
+	"strings"
+	"time"
+
+	"golang.org/x/xerrors"
+)
+
+const etcLocaltime = "/etc/localtime"
+const zoneInfoPath = "/var/db/timezone/zoneinfo/"
+
+// TimezoneIANA attempts to determine the local timezone in IANA format.
+// If the TZ environment variable is set, this is used.
+// Otherwise, /etc/localtime is used to determine the timezone.
+// Reference: https://stackoverflow.com/a/63805394
+// On Windows platforms, instead of reading /etc/localtime, powershell
+// is used instead to get the current time location in IANA format.
+// Reference: https://superuser.com/a/1584968
+func TimezoneIANA() (*time.Location, error) {
+	loc, err := locationFromEnv()
+	if err == nil {
+		return loc, nil
+	}
+	if !xerrors.Is(err, errNoEnvSet) {
+		return nil, xerrors.Errorf("lookup timezone from env: %w", err)
+	}
+
+	lp, err := filepath.EvalSymlinks(etcLocaltime)
+	if err != nil {
+		return nil, xerrors.Errorf("read location of %s: %w", etcLocaltime, err)
+	}
+
+	// On Darwin, /var/db/timezone/zoneinfo is also a symlink
+	realZoneInfoPath, err := filepath.EvalSymlinks(zoneInfoPath)
+	if err != nil {
+		return nil, xerrors.Errorf("read location of %s: %w", zoneInfoPath, err)
+	}
+
+	stripped := strings.Replace(lp, realZoneInfoPath, "", -1)
+	stripped = strings.TrimPrefix(stripped, string(filepath.Separator))
+	loc, err = time.LoadLocation(stripped)
+	if err != nil {
+		return nil, xerrors.Errorf("invalid location %q guessed from %s: %w", stripped, lp, err)
+	}
+	return loc, nil
+}
diff --git a/coderd/util/tz/tz_linux.go b/coderd/util/tz/tz_linux.go
new file mode 100644
index 0000000000..06d7bfe648
--- /dev/null
+++ b/coderd/util/tz/tz_linux.go
@@ -0,0 +1,44 @@
+//go:build linux
+
+package tz
+
+import (
+	"path/filepath"
+	"strings"
+	"time"
+
+	"golang.org/x/xerrors"
+)
+
+const etcLocaltime = "/etc/localtime"
+const zoneInfoPath = "/usr/share/zoneinfo"
+
+// TimezoneIANA attempts to determine the local timezone in IANA format.
+// If the TZ environment variable is set, this is used.
+// Otherwise, /etc/localtime is used to determine the timezone.
+// Reference: https://stackoverflow.com/a/63805394
+// On Windows platforms, instead of reading /etc/localtime, powershell
+// is used instead to get the current time location in IANA format.
+// Reference: https://superuser.com/a/1584968
+func TimezoneIANA() (*time.Location, error) {
+	loc, err := locationFromEnv()
+	if err == nil {
+		return loc, nil
+	}
+	if !xerrors.Is(err, errNoEnvSet) {
+		return nil, xerrors.Errorf("lookup timezone from env: %w", err)
+	}
+
+	lp, err := filepath.EvalSymlinks(etcLocaltime)
+	if err != nil {
+		return nil, xerrors.Errorf("read location of %s: %w", etcLocaltime, err)
+	}
+
+	stripped := strings.Replace(lp, zoneInfoPath, "", -1)
+	stripped = strings.TrimPrefix(stripped, string(filepath.Separator))
+	loc, err = time.LoadLocation(stripped)
+	if err != nil {
+		return nil, xerrors.Errorf("invalid location %q guessed from %s: %w", stripped, lp, err)
+	}
+	return loc, nil
+}
diff --git a/coderd/util/tz/tz_test.go b/coderd/util/tz/tz_test.go
new file mode 100644
index 0000000000..35f64843e4
--- /dev/null
+++ b/coderd/util/tz/tz_test.go
@@ -0,0 +1,40 @@
+package tz_test
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/coder/coder/coderd/util/tz"
+)
+
+//nolint:paralleltest // Environment variables
+func Test_TimezoneIANA(t *testing.T) {
+	//nolint:paralleltest // t.Setenv
+	t.Run("Env", func(t *testing.T) {
+		t.Setenv("TZ", "Europe/Dublin")
+
+		zone, err := tz.TimezoneIANA()
+		assert.NoError(t, err)
+		if assert.NotNil(t, zone) {
+			assert.Equal(t, "Europe/Dublin", zone.String())
+		}
+	})
+
+	//nolint:paralleltest // UnsetEnv
+	t.Run("NoEnv", func(t *testing.T) {
+		oldEnv, found := os.LookupEnv("TZ")
+		if found {
+			require.NoError(t, os.Unsetenv("TZ"))
+			t.Cleanup(func() {
+				_ = os.Setenv("TZ", oldEnv)
+			})
+		}
+
+		zone, err := tz.TimezoneIANA()
+		assert.NoError(t, err)
+		assert.NotNil(t, zone)
+	})
+}
diff --git a/coderd/util/tz/tz_windows.go b/coderd/util/tz/tz_windows.go
new file mode 100644
index 0000000000..0aedca5f77
--- /dev/null
+++ b/coderd/util/tz/tz_windows.go
@@ -0,0 +1,55 @@
+// go:build windows
+
+package tz
+
+import (
+	"os/exec"
+	"strings"
+	"time"
+
+	"golang.org/x/xerrors"
+)
+
+// cmdTimezone is a Powershell incantation that will return the system
+// time location in IANA format.
+const cmdTimezone = "[Windows.Globalization.Calendar,Windows.Globalization,ContentType=WindowsRuntime]::New().GetTimeZone()"
+
+// TimezoneIANA attempts to determine the local timezone in IANA format.
+// If the TZ environment variable is set, this is used.
+// Otherwise, /etc/localtime is used to determine the timezone.
+// Reference: https://stackoverflow.com/a/63805394
+// On Windows platforms, instead of reading /etc/localtime, powershell
+// is used instead to get the current time location in IANA format.
+// Reference: https://superuser.com/a/1584968
+func TimezoneIANA() (*time.Location, error) {
+	loc, err := locationFromEnv()
+	if err == nil {
+		return loc, nil
+	}
+	if !xerrors.Is(err, errNoEnvSet) {
+		return nil, xerrors.Errorf("lookup timezone from env: %w", err)
+	}
+
+	// https://superuser.com/a/1584968
+	cmd := exec.Command("powershell.exe", "-NoLogo", "-NoProfile", "-NonInteractive")
+	// Powershell echoes its stdin so write a newline
+	cmd.Stdin = strings.NewReader(cmdTimezone + "\n")
+
+	outBytes, err := cmd.CombinedOutput()
+	if err != nil {
+		return nil, xerrors.Errorf("execute powershell command %q: %w", cmdTimezone, err)
+	}
+
+	outLines := strings.Split(string(outBytes), "\n")
+	if len(outLines) < 2 {
+		return nil, xerrors.Errorf("unexpected output from powershell command %q: %q", cmdTimezone, outLines)
+	}
+	// What we want is the second line of output
+	locStr := strings.TrimSpace(outLines[1])
+	loc, err = time.LoadLocation(locStr)
+	if err != nil {
+		return nil, xerrors.Errorf("invalid location %q from powershell: %w", locStr, err)
+	}
+
+	return loc, nil
+}