Time Converter — Tips & Tricks
Strategy and pitfalls for the Time Converter: seconds vs. milliseconds, the inverted POSIX signs of the Etc/GMT zones, and reading Timeago units right.
Back to overview: Time Converter · Open the live tool: www.jpkc.com/tools/time/
The Time Converter is quick to operate — but time, time zones, and timestamps hide a few classic traps. This page collects what matters in practice. The technical groundwork is in the manual.
Seconds, not milliseconds
The most common pitfall: the Time Converter works with Unix timestamps in seconds (10 digits for current dates). Many systems — JavaScript first and foremost (Date.now()) — return milliseconds (13 digits), though. Enter a 13-digit millisecond number and you end up thousands of years in the future. Rule of thumb: if your value has 13 digits, divide it by 1000 before entering it. A current seconds timestamp has 10 digits today.
The Etc/GMT signs are the wrong way round
A genuine classic: the Etc/GMT zones follow the POSIX convention and therefore carry the opposite sign to the familiar UTC notation. Selecting Etc/GMT+1 actually yields UTC−1 (one hour behind Greenwich), and Etc/GMT-5 yields UTC+5. So choosing "GMT+1" for Central Europe gives you exactly the opposite. Remember: with the Etc/GMT entries, mentally flip the sign — or just pick CET for Central Europe.
The curated time-zone list knows no cities
The picker offers generic abbreviations (CET, EET, PST8PDT …) and Etc/GMT offsets — no IANA city zones like Europe/Berlin or America/New_York. Some of the generic abbreviations (e.g. CET, EST5EDT, PST8PDT) account for daylight saving, whereas the plain Etc/GMT offsets don't — they're fixed shifts with no DST switch. If you care about a specific city's DST-accurate local time, check the result deliberately and pick an abbreviation with the right DST behavior.
Timeago: each line is a total
Read the Timeago output correctly: the lines Years, Months, Day, Hours, Minutes, Seconds are not a decomposition of a single gap, but each the full distance in that one unit. "Months: 14" and "Day: 425" describe the same period, measured once in months and once in days. If you want the decomposed form "X years, Y months, Z days", use the precise breakdown on the last line.
Time zone and language apply to all tabs
Language Format and Timezone sit in the card footer and act on Current, Convert, and Timeago at once. So set them before converting. Note: the language changes only the formatting, not the instant; the time zone changes only the display, not the underlying Unix timestamp (which is why line 1 stays the same across all time zones).
Pause the live clock to copy
In the Current tab the clock ticks on every second — awkward when you want to select a value calmly. Click Start/Stop Timer to freeze the display, copy the value (or use the clipboard button), then start it again. The output field is also editable, in case you want to adjust a value before copying.
Server time as an independent reference
If you doubt your local machine clock, grab the server clock's timestamp with Get Server Time in the Convert tab. That way you spot a mis-set local clock before it feeds you wrong conversions. For your own scripts the two endpoints /tools/time/time/ (seconds) and /tools/time/mtime/ (microtime) are available directly as plain text.
Combine with other JPKCom tools
- Cron generator — when you don't just want to convert a single moment but formulate a recurring schedule; convert the next run back into a readable date here.
- UUID generator — time-based UUIDs (v1, v7) carry a timestamp inside them; use the Time Converter to place it.
- Hash generator — for time-stamped records whose integrity you want to secure with a checksum.
The full function reference is in the manual, concrete walkthroughs in the examples. You can try everything in the tool.