DateTimeMate - Terminal-styled date/time calculator with sub-second precision for devs and sysadmins

Hey everyone! I'm a sysadmin/developer who got tired of juggling between date, Wolfram Alpha, and timeanddate.com every time I needed to answer stuff like "how long between these two timestamps?" or "what date is 3 weeks and 4 days from now?" None of the existing tools did everything I wanted, so I built one.

It started as a Go library and CLI tool, but I figured why not throw a web UI on it too. It's got an old-school green-on-black terminal look. 😎

Here's what you can do with it:

• Date diff -- How long between two dates/times? Works down to nanosecond precision, and you can use stuff like now, yesterday, tomorrow as inputs (UTC-based)
• Date math -- Add or subtract durations from a date. A useful feature: you can repeat it ("give me every 2-week interval for the next 6 months") or run until a target date
• Duration conversion -- Ever wonder how many weeks/days/hours 25,771,401 seconds is? It's 42 weeks 4 days 6 hours 43 minutes 21 seconds. Now you don't have to wonder.
• Date reformatting -- Reformat dates with strftime specifiers. Convert epoch timestamps to something readable and back again.

The thing that bugged me about every other date site out there is that none of them go below seconds. If you work with logs or telemetry data, you need milliseconds, microseconds, sometimes nanoseconds. This handles all of that.

It also supports a brief notation (1Y2M3W4D5h6m7s) so you can type fast and get compact output. No ads, no tracking, no sign-up because it's just a text box and some buttons.

The underlying Go library (DateTimeMate) works as a standalone CLI tool too if you'd rather stay in your terminal.

Check it out: https://datetimemate.com