Dates, timezones, and timestamps

Metra separates:

• calendar date (a day like 2026-09-02)
• exact time (a precise UTC instant)

This keeps due dates consistent for each site and keeps audit history exact.

Date and time types

Do not treat a date-only value as midnight in your own timezone. It is always the calendar day, not a full instant.

Site timezones

Each site has an IANA timezone such as Europe/London or UTC. Metra uses this timezone for:

• due state calculation,
• due date comparisons,
• notification timing.

So different sites can be in different due states at the same instant.

If a site timezone is invalid, due status checks can fail. Fix the site first rather than guessing from your workstation clock.

Metra-calculated date values

Metra calculates these values for you:

• current local date for the site
• current, due soon, due today, overdue, suspended
• warning windows
• notification trigger times
• validation of performed dates
• next due dates from approved calibration events

Do not recalculate these values outside the app.

Calendar intervals

Intervals are based on calendar behaviour:

• days and weeks add day counts,
• months and years follow real calendar boundaries.

Examples:

• 31 Jan + 1 month = 28/29/30 Feb (depends on year)
• 30 Nov + 3 months = 28/29 Feb
• 31 Mar + 1 month = 30 Apr

If a start day does not exist in the target month, Metra uses the last day of that month.

UTC timestamps and storage

Storage events use UTC for consistency:

• movement changes
• records and upload times
• approvals and submissions
• generation events
• audit events

Deployment intervals use half-open ranges: [effective_from, effective_until).

• start instant is included
• end instant is not included

If equipment leaves one site at 10:00 and arrives another at 10:00, the same instant belongs only to the new site.

Dossier periods and deployment overlap

Dossier start/end dates are inclusive.

For historical selection, Metra checks whether each equipment deployment overlaps the dossier period and client scope.

• If overlap exists, equipment is included.
• Events are included only when the event time is in-scope for included equipment.

This is why movement times at period boundaries are important.

How dates are shown in the app

• Calendar dates keep their day in display.
• Same timestamp can show different local times to different users.
• For strict ordering checks, use the UTC timestamp from source history.
• Exported evidence may show UTC explicitly.

Practical checklist

• Use a correct IANA timezone on each site.
• Enter performed dates at the site date when work happened.
• Enter movement times as exact instants.
• Treat dossier dates as inclusive.
• Trust Metra’s returned status values.

Related guides

• Manage sites and locations
• Understand due status
• Create a calibration requirement
• Record calibration work
• Equipment and rotation
• Select dossier scope