How do I convert between time units?

Convert through seconds as a base unit. 1 min = 60 s, 1 h = 3600 s, 1 day = 86,400 s, 1 week = 604,800 s, 1 month = 2,629,800 s (avg Gregorian month, 30.44 days), 1 year = 31,557,600 s (Julian year, 365.25 days). To convert from unit A to unit B: value_B = value_A × (seconds_per_A / seconds_per_B). Example: 5 days → minutes = 5 × (86,400 / 60) = 7,200 min.

How many seconds are in a year?

A Julian year (365.25 days, used in astronomy and ESA orbital mechanics) = 31,557,600 s. A common Gregorian year (365 days) = 31,536,000 s. A leap year (366 days) = 31,622,400 s. The civil-time average over the 400-year Gregorian cycle is 31,556,952 s/year. NASA Voyager 1 MET (launched 1977-09-05) exceeded 1.5 billion seconds in 2025 — about 48 Julian years.

Why is one month 30.44 days on average?

The Gregorian calendar averages 30.4368 days per month over the 400-year cycle (365.2425 days/year ÷ 12 = 30.43687 days/month). This tool uses 30.44 days = 2,629,800 s. Specific months vary: February (28 or 29), April/June/September/November (30), the rest (31). Astronomers prefer to avoid "month" entirely and use Julian days for unambiguous calculations.

How many minutes are in a week?

1 week = 7 days × 24 h × 60 min = 10,080 minutes. 1 month ≈ 43,830 min (using 30.44 avg). 1 year (Julian) ≈ 525,960 min. The Broadway musical "Rent" immortalized the 525,600 figure (Gregorian common year). For payroll, scheduling, and project-management tools (Asana, Jira, Monday.com), the week-in-minutes count anchors capacity planning.

What is the difference between Julian and Gregorian years?

The Julian year (365.25 days) is the astronomical reference, used by IAU and ESA. The Gregorian calendar (Pope Gregory XIII, 1582) averages 365.2425 days/year by inserting 97 leap days per 400 years (skipping years divisible by 100 but not 400 — so 1900 was NOT leap; 2000 WAS). The 0.0075-day difference per year (10.8 min) accumulates to about 3 days every 400 years.

How do I convert seconds to years?

Divide by 31,557,600 (Julian year) or 31,536,000 (common Gregorian year). 1 billion seconds ≈ 31.69 Julian years. 1 trillion seconds ≈ 31,688 years (longer than recorded history). The Earth's age (4.54 billion years) ≈ 1.43 × 10^17 seconds. The current age of the universe (13.8 billion years) ≈ 4.36 × 10^17 seconds.

How many hours in a month?

Average Gregorian month (30.44 days) = 730.5 hours. Specific months: 28 days = 672 h, 29 days = 696 h, 30 days = 720 h, 31 days = 744 h. Full-time work month (4 weeks × 40 h) = 160 working hours. The IRS FLSA standard month for overtime threshold uses 173.33 hours (2080/12) — the per-month decimal-hour figure for salary-to-hourly conversion.

Why does this tool use Julian years instead of Gregorian?

The Julian year (365.25 days = 31,557,600 s) is the IAU astronomical standard and the SI-approved conversion factor. The Gregorian average (365.2425 days = 31,556,952 s) differs by only 648 seconds (0.002%) per year. For most user purposes the difference is negligible; this tool uses Julian for consistency with NASA, ESA, JAXA, and the U.S. Naval Observatory ephemerides.

How are time units defined in the SI system?

Only the second is an SI base unit (defined as 9,192,631,770 cesium-133 hyperfine transitions, 13th CGPM 1967, refined 2019). Minute, hour, day are "units accepted for use with SI" per the SI Brochure 9th edition (2019). Week, month, year are NOT SI-accepted but are widely used in civil contexts. Astronomers prefer Julian dates (continuous days since 4713 BCE January 1) for unambiguous calculation.

How do I handle leap seconds in unit conversion?

This tool ignores leap seconds — it treats a day as exactly 86,400 s. The IERS has inserted 27 positive leap seconds since 1972 to keep UTC aligned with Earth's slowing rotation. The 27th CGPM Resolution 4 (November 2022) voted to abolish leap seconds by or before 2035 — making the 86,400 s/day assumption permanently true. Until then, exact-to-the-second UTC arithmetic must consult IERS Bulletin C.

What is the natural unit hierarchy for time?

From smallest to largest: Planck time (5.39 × 10⁻⁴⁴ s, theoretical) → attosecond (10⁻¹⁸ s, attosecond chemistry Nobel 2023) → nanosecond (10⁻⁹ s, HFT trading) → microsecond → millisecond → SECOND (SI base) → minute → hour → day → week → month → year → decade → century → millennium → kalpa (4.32 billion years, Hindu cosmology). This tool covers second through year.

Why are seven distinct time units shown?

Seconds for SMPTE timecode and Unix epochs. Minutes for Pomodoro and fitness apps. Hours for payroll and aviation. Days for project schedules and Julian dates. Weeks for sprint planning (Agile, Scrum). Months for billing cycles and HR analytics. Years for cumulative MET, mortgage amortization, and longitudinal studies. Each unit dominates one industry — this tool lets you pivot between them in one keystroke.

Universal Time Unit Converter (s · min · h · d · wk · mo · yr)

To convert between time units, pass through seconds as a base: 1 min = 60 s, 1 h = 3600 s, 1 day = 86,400 s, 1 week = 604,800 s, 1 month = 2,629,800 s (Gregorian avg 30.44 d), 1 year = 31,557,600 s (Julian 365.25 d). Type ONE value in ANY unit — all seven others compute simultaneously, rendered on a nested-concentric-circles widget showing relative scale.

Widget

nested circles

Units

7 simultaneous

Year basis

Julian 365.25 d

Worked example

1 h → all 6

Quick Conversion

FROM (hours)

TO (days)2

Formula: days = hours / 24

Nested-Circles Scale Atlas + Seven-Unit Synchronizer

Input

All Seven Units (simultaneous)

Seconds

3,600

Minutes

min

Hours

Days

0.041667

Weeks

0.005952

Months

0.001369

Years

0.000114

Conversion basis: 1 mo = 30.44 d (Gregorian avg), 1 yr = 365.25 d (Julian, IAU standard). Active unit highlighted in amber.

Quick-Pivot Presets

Cross-Unit Reference Matrix (per 1 unit)

1 of...	s	min	h	d	wk	mo	yr
1 s	—	0.016667	0.000278	1.1574e-5	1.6534e-6	3.8026e-7	3.1688e-8
1 min	60	—	0.016667	0.000694	9.9206e-5	2.2815e-5	1.9013e-6
1 h	3,600	60	—	0.041667	0.005952	0.001369	0.000114
1 d	86,400	1,440	24	—	0.142857	0.032854	0.002738
1 wk	604,800	10,080	168	7	—	0.229979	0.019165
1 mo	2.6298e+6	43,830	730.5	30.4375	4.3482	—	0.083333
1 yr	3.1558e+7	525,960	8,766	365.25	52.1786	12	—

Need direct conversions? See Time → Seconds or Seconds → Time.

Formula

value_B = value_A × (seconds_per_A / seconds_per_B)

Worked: 5 days → minutes. seconds_per_day = 86,400. seconds_per_minute = 60. Result = 5 × (86,400 / 60) = 7,200 min. The nested-circles widget highlights the active ring; all other rings update on input.

How to Use the Universal Converter

Type a value in the input box (any positive number, decimals OK).
Select the source unit from the dropdown — second, minute, hour, day, week, month, or year.
Watch the nested-circles widget — the chosen ring fills with amber; all seven outputs compute simultaneously.
Read the seven-unit output panel — the active row glows amber; the other six show the converted values.
Save to history — persist your conversions to localStorage for repeat project-cycle queries.

Why Seven Time Units Coexist — From Cesium to Calendars

In 2026, a senior consultant at a global logistics firm needs to convert "320 hours of project burn" into days for the schedule, weeks for the sprint board, months for the executive summary, AND years for the longitudinal report — all in one input. Seven time units coexist because each industry locked in a different default: seconds for telemetry, minutes for Pomodoro, hours for payroll, days for projects, weeks for Agile, months for billing, years for amortization. This tool exists to pivot between them in one keystroke.

The 60-second minute and 60-minute hour are Babylonian sexagesimal inheritances from ~1800 BCE. Clay tablets from Old Babylonian Nippur record arithmetic in base-60 because 60 has twelve divisors. Greek astronomy (Hipparchus 190-120 BCE) divided the day into 24 hours; Ptolemy's Almagest (~150 CE) split each hour into 60 minutes (Latin pars minuta prima) and each minute into 60 seconds (pars minuta secunda) — the convention this tool still uses.

The 7-day week is older than the sexagesimal day — Babylonian astronomers correlated it with the seven visible "wandering stars" (Sun, Moon, Mars, Mercury, Jupiter, Venus, Saturn). Roman planetary-day naming (Dies Solis, Lunae, Martis...) became Germanic-named days (Sunday, Monday, Tuesday...). The 7-day week was codified globally by Constantine's 321 CE edict and survives because no commercial or religious system has successfully replaced it — the French Revolution's 10-day décade (1793-1805) failed.

The mechanical chronograph (Peter Henlein, Nuremberg, ~1505) baked the 60-base into European civil life. Christiaan Huygens' pendulum clock (1656) added per-second precision. The Gregorian calendar (Pope Gregory XIII, 1582) refined the Julian-year approximation: instead of 365.25 days/year, Gregorian averages 365.2425 by inserting 97 leap days per 400 years (skipping years divisible by 100 but not 400 — 1900 was NOT leap, 2000 WAS).

NIST timekeeping defines the SI second precisely (9,192,631,770 cesium-133 hyperfine transitions per the 13th CGPM, 1967, refined 2019). NIST-F2 cesium-fountain (Boulder, CO, operational 2014) drifts less than one second per 300 million years. Per the SI Brochure 9th edition (2019), only the second is an SI base unit; minute, hour, day are "accepted for use with SI"; week, month, year are NOT formally SI-accepted but are civil-time defaults.

ISO 8601:2019 §4.4 defines duration syntax: P1Y2M3DT4H5M6S means "period 1 year 2 months 3 days, 4 hours 5 minutes 6 seconds". The Y, M, W, D, H, M, S markers cover six of this tool's seven units. Calendar APIs (Microsoft Graph, Google Calendar, Apple EventKit), database fields (PostgreSQL INTERVAL, MySQL TIMESTAMPDIFF), and project-management tools (Jira, Asana, Linear) all internally use ISO 8601 duration with these markers.

The Julian year (365.25 days = 31,557,600 s) is the IAU astronomical standard used by NASA, ESA, JAXA, and the U.S. Naval Observatory. NASA Voyager 1 MET (launched 1977-09-05) exceeded 48 Julian years (1.5+ billion seconds) by 2026. Hindu cosmology defines a Kalpa as 4.32 billion years — 1.36 × 10^17 SI seconds, longer than the projected lifetime of low-mass stars. This tool covers seven of the most commercially used units; drilling down to seconds is one click away.

Time Unit Conversion FAQs

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