Dates, Timestamps, and Time Zones

A date and an instant are not the same thing. “Monday at 9” needs a time zone before two people in different places can agree on when it happens. A Unix timestamp, by contrast, points to one instant.

Keep the zone with the time

When arranging a meeting or reading a log, record the time zone or UTC offset alongside the clock time. An offset like +07:00 describes that one timestamp; a named zone can also account for rule changes and daylight saving time.

Watch boundaries

Adding 24 hours is not always the same as moving to the same local clock time tomorrow when daylight saving changes. For schedules, check the result around a zone’s transition dates instead of assuming every day has the same number of local hours.

Related tools

• Age Calculator — Work out an age in years, months and days, with totals and the next birthday.
• Chronometer — A simple stopwatch with laps.
• Date Calculator — Add or subtract days, weeks, months and years, or measure the duration and business days between two dates.
• ETA Calculator — Estimate a finish time from progress, elapsed time and remaining work.
• Percentage Calculator — Work out percentages, increases and decreases.
• Time Zone Converter — Read a timestamp from a log and see the same moment in UTC, Jakarta and other zones.
• Timestamp Converter — Convert between Unix timestamps, ISO strings and local time.
• User Agent Parser — Read the browser, engine, OS and device from a user-agent string.