Calendar and date tools
Date math, calendar files, and time zone planning — computed in your browser.
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Most popular
All calendar tools
Make a calendar file that opens in Google Calendar, Outlook, or Apple Calendar.
Count the days, weeks, and months between two dates.
Exact age in years, months, and days, plus the next birthday.
Build a live countdown and share it as a link.
Count working days between two dates, skipping weekends and holidays.
Expand a repeat rule into dates and export them as one calendar file.
Line up one meeting time across several time zones and share the view.
Convert between ISO 8601, Unix timestamps, and human-readable dates.
Find which weekday any date falls on, past or future.
About these tools
Date arithmetic looks trivial and is not. Months have different lengths, years have different lengths, clocks shift twice a year in most of the world but not the same weekend everywhere, and the "obvious" way to add a month to 31 January produces a date in March. Every tool in this category works on calendar dates as whole units rather than on elapsed milliseconds, which is what makes the answers exact across daylight saving changes and leap years alike.
Time zone conversion uses your browser’s own copy of the IANA time zone database — the same source calendar software reads — so offsets are correct for the specific date being asked about rather than for today. That distinction is what catches out meetings scheduled in the weeks each spring when different regions have moved their clocks out of step.
Nothing here needs a server, and nothing is stored. The two tools that produce shareable links encode the whole thing in the URL rather than saving it somewhere, which means the link cannot expire and there is no record of it to leak. Calendar files are assembled as text in your browser and handed straight to your downloads folder.
FAQ
What is an .ics file and which apps can open one?
A plain-text calendar file in the iCalendar format defined by RFC 5545. Google Calendar, Outlook, Apple Calendar, Thunderbird, and essentially every other calendar application can open one, which is why it is the standard way to send an event to someone on a different system.
Do these tools handle daylight saving time correctly?
Yes. Offsets are read from your browser’s IANA time zone database for the exact date in question, so a conversion in March reflects whichever regions had already moved their clocks by then.
Which public holidays are built in?
US federal holidays and England & Wales bank holidays, both computed from the rules that define them rather than a stored list, so they stay correct in future years. Everything else is entered as your own dates — a transcribed holiday table that quietly goes stale is worse than one you supplied.
Do the shareable links expire?
No. The countdown and time zone links carry all their data in the URL, so there is nothing stored that could be deleted or time out.