Date and Time Tools

Dates are the part of programming and of ordinary life that everybody assumes is simple and nobody gets right. Months have different lengths, years occasionally have an extra day, clocks jump forward and back twice a year in some countries and never in others, and time zones are a political fact rather than a mathematical one.

The tools here take that seriously rather than papering over it. The timestamp converter works in both directions, detects whether a number is in seconds or milliseconds, and shows the result as ISO 8601 in UTC, in a time zone you pick from your browser’s own list, and as a relative time such as three hours ago. Where a calculation has to make a choice — what one month after 31 January means, what happens to a wall-clock time that a daylight-saving jump deleted — the tool states which convention it used instead of quietly picking one.

All of it runs on your own device using the date and internationalisation support already built into your browser, so there is no lookup service to be down, no rate limit, and nothing about the dates you are checking that leaves the page.