Epoch Math
Add or subtract any unit from a Unix timestamp, ISO date, or the keyword now. Chain operations and copy the result in Unix, ISO 8601, or human formats.
Frequently asked questions
How do I add days to a Unix timestamp?
Type the timestamp, then a plus sign, then the amount and a unit. Example: 1748876543 + 7d adds seven days. You can chain operations: now + 1h - 30m subtracts 30 minutes from one hour from now. Units accepted are s, m, h, d, w, mo, and y.
What units does this calculator support?
Seconds (s), minutes (m), hours (h), days (d), weeks (w), months (mo), and years (y). Use "mo" for months — single "m" is reserved for minutes to avoid ambiguity. Numbers can be any integer; for example 90d adds 90 calendar days.
Does this handle DST and calendar-aware month math correctly?
Yes. The calculator uses the Luxon date library, which uses the IANA time zone database. Adding "1mo" lands on the same day of the next month (with day-clamping at month-end) rather than a flat 30 days. Adding "1d" across a DST boundary correctly accounts for the gained or lost hour.
Can I do millisecond math?
Yes. If you pass a 13-digit Unix timestamp it is treated as milliseconds; 10-digit values are treated as seconds. The result panel always shows both forms so you can copy whichever your code expects.
Are negative timestamps and pre-1970 dates supported?
Yes. Subtracting more than the starting timestamp produces a negative Unix value, which represents a date before 1970-01-01 UTC. The human-readable rendering still works correctly for those dates (within the year range Luxon supports).
What does "now" mean exactly?
The exact moment the page evaluates the expression — to the millisecond. The result is computed in your browser, not on a server, so "now" is your local clock's read of the current Unix time. The accompanying datetime line shows the UTC equivalent for clarity.