units
convert between every unit of time
── about this calculator ──
The unit converter answers the everyday question "how many X are in Y?" for every common unit of time, from milliseconds up to years. Type a number, pick the unit you started with, and read every other unit at once. The currently-selected source row is highlighted so you can confirm at a glance.
Two conventions to keep in mind: a "month" here means exactly 30 days, and a "year" means exactly 365 days. These are standard simplifications used in physics, billing, and most SLA documents because real calendar months and leap years don't have a single numeric value. If you need calendar-aware math — for example "what date is six months from today?" — use the date-math calculator instead, which uses your browser's actual calendar logic.
── frequently asked ──
- › Why does the converter use 30-day months and 365-day years?
- Months and years are not fixed-length, but for unit conversion you need a single number. We use the common simplifications: 1 month = 30 days, 1 year = 365 days. For exact calendar math (e.g. 'add 6 months to this specific date'), use the date-math calculator instead.
- › How precise is the conversion?
- Internally we work in seconds (with millisecond support). Displayed values are rounded to six decimal places, or shown in scientific notation when extremely small.
- › Can I convert to and from milliseconds?
- Yes. Pick milliseconds in the dropdown to start from a millisecond value, and read the millisecond row to convert any other unit into ms. This is handy when working with JavaScript timestamps or animation frame timings.
- › What about leap seconds?
- Leap seconds are not used by this calculator. They're applied irregularly to civil time and are usually invisible at the second-counting level — only deeply specialized work (astronomy, GPS) needs to account for them.