Times & timezones

Every time WatchTower15 records is an instant: a moment in UTC, the same moment for everyone. What changes from person to person is only how it is shown.

How times are shown

Every time on screen is shown in your display timezone and says which timezone that is. A table column names the zone in its header (Date & Time (BST)); a chart names it in its corner; the time-range selector says it in its footer, for example Times in Europe/London (BST, UTC+01:00) · Dates as DD/MM/YYYY. Hover over a time to see it in full, with the same moment in UTC beside it.

Times use the 24-hour clock. Numeric dates follow your date format, such as day first (06/10/2026), month first (10/06/2026) or year first (2026-10-06), and the selector footer always says which one you are reading. The Audit page and the incident lists give each time to the second, in a Date & Time column: 06/10/2026, 14:03:22.

When a window crosses a change of clocks, such as the end of summer time, a chart names both zones (BST → GMT), and a row whose time is in the other zone prints its own.

Setting your timezone and date format

Open Profile → Preferences:

• Timezone: Browser (the default) follows the timezone of the browser you are using; UTC or a named zone (Europe/London, America/New_York) fixes it wherever you are.

• Date format: From my browser (the default) follows your browser’s language settings, or choose one of six formats to fix it:

  Format	6 October 2026 reads
  DD/MM/YYYY	06/10/2026
  MM/DD/YYYY	10/06/2026
  YYYY-MM-DD	2026-10-06
  YYYY/MM/DD	2026/10/06
  DD-MM-YYYY	06-10-2026
  MM-DD-YYYY	10-06-2026

  From my browser shows the format it picked, such as From my browser (DD/MM/YYYY): the one your browser’s language writes when it is one of the six (en-GB reads DD/MM/YYYY, en-US MM/DD/YYYY, sv-SE YYYY-MM-DD, ja-JP YYYY/MM/DD). A language that writes dates another way gets the nearest: year first reads YYYY-MM-DD, month before day MM/DD/YYYY, and anything else DD/MM/YYYY, so de-DE’s 06.10.2026 reads 06/10/2026.

The card previews the current time as it will be shown. Your choice applies to every date on every page, chart axes included, and a named timezone also to the alarm emails sent to you (see below). It is yours alone: everyone in your organisation sets their own.

A server’s own timezone

On a server’s page, every time-range selector carries a zone switch: on Overview, Logs, Storage, Network, Processes, System services, Custom metrics and Incidents. Open Custom: the footer of its panel, after Times in …, offers three zones, in place of the Change link to your profile that other pages show there:

• My timezone: your display timezone, as everywhere else.
• Server’s timezone: the zone the server itself reports, so its charts and log lines read as they do on the machine. It is greyed out, with the reason, when the server has not reported a zone.
• UTC.

Your choice takes effect at once and applies to the whole page, whichever selector you made it in: every tab, chart, log line and drawer. The tabs with no time range of their own, Alarms, Info and Audit, follow the zone last chosen in any selector on the page, or your display timezone until you choose one. The Clock card’s Time in the server’s zone is always in the server’s zone. The choice stays as you leave it in this tab, on every server’s page, for you and this organisation only.

The Clock card

The server’s Info tab has a Clock card, from what the agent reports:

Row	What it shows
Server timezone	The zone’s name, its abbreviation and its offset from UTC. A server whose agent reports no zone name shows the abbreviation and offset alone.
Time in the server’s zone	The current time in that zone.
Clock synchronised	Whether the server’s clock is kept in time, and by which time service (chronyd, systemd-timesyncd…).
Clock accuracy	How far the server’s clock may be off, in milliseconds.
Offset from WatchTower15	How far the server’s clock is from WatchTower15’s: In sync (within 2 seconds), 42 s fast or 42 s slow, 7 min fast · corrected by the agent when the agent already corrects the times it sends by that much, 7 min fast — rejected while WatchTower15 is rejecting the server’s data for it, or Unknown. The agent’s own measurement against WatchTower15’s answers when it reports one, else WatchTower15’s measurement of the agent’s requests.
Booted at	When the server started, by its own clock.

An agent older than the one that reports the clock shows Not reported by this agent version: upgrade the agent to see it. The uptime in the server’s header is measured on WatchTower15’s clock, so a server whose clock is wrong still shows the right uptime.

Time windows

The time-range selector is the same on every page that has one: the last 1h, 3h, 12h, 1d or 5d, then Custom, which takes a length of your own, such as the last 2 weeks, or dates on the calendar.

• A relative window ends at WatchTower15’s clock, when the data is fetched, not at your computer’s: the last 3 hours is the same three hours however far your computer’s clock is off.
• A window that reaches back further than the data is kept starts at the oldest data kept. Logs, for example, are kept for 30 days, so a server’s Logs tab on a 6-week range searches the last 30 days, and says so.

Days and billing dates are UTC

A day in WatchTower15 runs from 00:00 to 24:00 UTC, wherever you are:

• the uptime strips on domains and services, one bar per UTC day;
• billing periods, invoice dates and the dates a courtesy period starts and ends;
• daily usage and the log allowance, which start again on the invoice date at 00:00 UTC.

These dates are labelled (UTC) on screen, so a day never shifts because of where you are reading it.

Emails, SMS and chat messages

An alarm email gives the time of the event in UTC and, when Profile → Preferences names a timezone other than UTC, the same moment in that zone in brackets: Triggered 6 Oct 2026, 13:03 UTC (14:03 BST). With Browser chosen, the email gives UTC alone, since an email cannot know your browser’s zone. Emails write the month in words, so the date reads the same whatever your date format.

SMS and chat messages end with the event’s time in UTC: Triggered at 13:03 UTC.

The API

Every time the API returns is epoch milliseconds: a whole number of milliseconds since 1 January 1970 UTC, for example 1791291780000 for 6 October 2026 at 13:03 UTC. That includes time-series points and the window_from and window_to of a series. Calendar dates, such as an invoice’s period_start or a domain’s registration expiry_date, stay YYYY-MM-DD strings.

Every time the API accepts is epoch milliseconds, as a number or as a string of digits (a query parameter), or RFC 3339 with its offset (2026-10-06T13:03:00Z, 2026-10-06T14:03:00+01:00). A time with no offset is refused: it would mean a different moment in every timezone.

The two ingest APIs read their timestamps more loosely, so existing shippers keep working: see custom metric ingest and log ingest.

Asking for a time window

A request that reads a span of time, such as a chart’s series, a log search or the audit list, takes its window in one of two forms:

• period: the last stretch of time, a number from 1 to 9999 followed by m, h, d or w. period=3h is the last 3 hours and period=2w the last 2 weeks, ended by WatchTower15’s clock.
• from and to, always together: a fixed window, each end in epoch milliseconds or RFC 3339 with its offset, to after from. A to up to 5 minutes ahead of WatchTower15’s clock is read as now.

With neither, the request uses its own default: the last day for most charts, and everything kept for a list such as the audit list or a log search. A window that starts before the oldest data kept starts there instead. Sending period with from or to, or one of from and to alone, is refused with a 422, and so are these, each with its message:

Sent	Message
A period in any other form	The period must be a number from 1 to 9999 followed by m, h, d or w, such as 3h.
A to more than 5 minutes ahead of WatchTower15’s clock	The window ends in the future.
A to before the oldest data kept	The window ends before the oldest data kept (30 days)., naming that data’s retention

After an update

If a dashboard or any page was left open across a WatchTower15 update that changed how times are sent, reload it: a page loaded before the update can read the new times wrongly until it is reloaded.