Pick a calculator, shareable URLs, optional time zones.
Pick a start date and how many days to add. Turn on time and a custom time zone when you need wall-clock precision; otherwise we use noon in your zone to avoid daylight-saving surprises. Everything you set is reflected in the address bar for sharing.
Choose your anchor date and how many days to move backward. Add time-of-day and an explicit zone when it matters; the tool defaults to your browser zone. Your choices stay in the URL so you can bookmark or send the link.
Compare two dates for a simple day count, or enable hours and minutes for a real span, including different end zones when you override the clock. Plain calendar math when time is off; zone-aware instants when it is on. State lives in the query string.
Enter how many seconds or milliseconds you want to express. Switch the input to milliseconds when your value counts ms. Pick a full breakdown (approximate years and months) or a hours-focused summary. Your input and options stay in the URL.
Paste a Unix timestamp in seconds or flip the switch for milliseconds. We show a clear local-style date and time in your browser zone or a zone you choose. Copy the long form, ISO UTC, wall time, or raw seconds and milliseconds.
Pick the calendar date and time of day (seconds supported). Use the paste button next to the date to open a field where you paste with Ctrl+V (no browser permission). ISO, Unix, or yyyy-mm-dd. Toggle a custom IANA zone or use your browser zone. Copy seconds, milliseconds, or ISO UTC.
Free to use
Every tool here is free: no paywall, no account, no subscription. Just open a page and calculate.
Add days to a date moves a calendar date forward by whole days, with optional time of day and time zone and a shareable URL. Subtract days from a date moves backward from an anchor date the same way. Compare two dates counts calendar days between dates or, when time is enabled, measures a real elapsed span with zone-aware instants. Convert Unix timestamps to a readable date and time (seconds or milliseconds), pick a zone, and copy ISO or wall-clock forms. Turn a calendar date and optional clock time into Unix seconds or milliseconds. Break down a duration in seconds or milliseconds into years, months, days, and smaller units (approximate) or into a hours-focused view. Use the filters and interactive cards above to search, narrow down, and open any calculator.
