Conversion Runs locally Ready to use Built-in examples No tracking

Time Converter

Convert time units instantly, with the 30-day month and 365-day year conventions clearly stated.

Time units form one of the few mixed-radix systems: 1000 milliseconds to a second, 60 seconds to a minute, and then the jump to months carries 28 to 31 days of variation. Get one step wrong and a timeout threshold or a cache TTL is out by an order of magnitude. This tool converts between eight units from milliseconds to years, with the basis of each conversion stated and a single input filling the whole table.

The convention has to be explicit: a month is taken as 30 days and a year as 365, which is the engineering habit for estimation rather than the calendar's behaviour — real months run 28 to 31 days and years carry leap days. Interest, lease terms, seniority and anything legal or financial wants a date calculator working on the real calendar; this tool suits engineering magnitudes such as timeout thresholds, cache TTLs and request latency.

—

How to use

  1. Enter the duration and choose its unit.
  2. Read the full table of equivalents.
  3. Note the 30-day month and 365-day year conventions.
  4. Use a date calculator for legal or financial periods.

How it works

Fixed conversion conventions

Time units step by fixed factors: 1 minute = 60 s, 1 hour = 3600 s, 1 day = 86400 s, 1 week = 7 days. Conversion is pure multiply/divide with no approximation.

Why months and years use 30/365 days

"Month" and "year" have no fixed day count, so this tool uses the common approximate convention: 1 month = 30 days, 1 year = 365 days. Hence 1 year = 365 days = 8760 hours, while 12 months = 360 days — a 5-day gap. Financial interest and contract schedules often use the 360-day convention, so confirm before converting.

Common time constants

Common constants: 1 year is about 8760 hours, about 31,536,000 seconds; 1 day = 1440 minutes; 1 hour = 3600 s; 1 millisecond = 0.001 s. If unsure, enter 1 on the left and pick the unit to convert.

Code example

JavaScript Seconds as the hub, on an engineering convention 

const S = { ms: 0.001, s: 1, min: 60, h: 3600,
            d: 86400, week: 604800,
            month: 2592000,      // 30 days (engineering convention)
            year: 31536000 };    // 365 days

const convert = (v, from, to) => v * S[from] / S[to];

convert(1, "d", "ms");       // 86400000
convert(1, "year", "d");     // 365

Python timedelta only follows the real calendar 

from datetime import timedelta

timedelta(days=30).total_seconds()   # 2592000.0

# Note: timedelta has no month or year (their day counts vary);
# use dateutil.relativedelta for real-calendar arithmetic:
from dateutil.relativedelta import relativedelta
# relativedelta(months=3) handles long/short months and leap years

FAQ

Why is a year 365 days and a month 30 days?

It's the common approximation after rounding the Gregorian calendar, for uniform engineering and financial calculation. Real years are 365/366 days and natural months 28-31 days, so results differ from the calendar by 0-3 days.

Is a year 8760 hours or 8640 hours?

Under this tool's convention (365 days) it's 8760 hours; under the business convention "12 months x 30 days = 360 days" it's 8640 hours — a 120-hour gap. Confirm the convention before interest or schedule calculation.

Where does the definition of a second come from?

The modern second is the duration of 9,192,631,770 cycles of a specific transition of the cesium-133 atom, an atomic-time standard. "1 day = 86400 seconds" approximates a mean solar day, with leap seconds correcting the real value.

Why are hours, minutes and seconds base 60?

From the ancient Babylonian sexagesimal timing tradition, carried down to today. 60 divides evenly by 2, 3, 4, 5, 6, 10, 12, 15, 20 and 30 — very convenient for splitting time, more practical than base 10.

Are milliseconds, microseconds and nanoseconds all 1000-based?

Yes. 1 second = 1000 milliseconds = 10^6 microseconds = 10^9 nanoseconds. This tool covers down to milliseconds; microseconds and nanoseconds, discussed in program performance and network latency, are smaller scales.

Can it help with work schedules or overtime hours?

It converts total duration, but business rules like "working days vs. calendar days" and holidays need separate handling. Compute total days or hours first, then subtract weekends and holidays with the workday calculator — the two together are more accurate.

Does this conversion need a network connection?

No. Conversion uses only constants (60, 3600, 86400, and so on) and works offline once the page loads. Given it may involve contracts and wages, we upload nothing; records stay in your browser and can be cleared anytime.