MATLAB datenum Converter

Q: What is MATLAB datenum?

A count of **days since Jan 0, 0000** (i.e. 1 = 0000-01-01). Modern dates are ~740,000. The fractional part is time of day.

Q: What is Mathematica AbsoluteTime?

Seconds since **1900-01-01 00:00:00**, as an integer. 2026-08-13 ≈ 3,996,000,000 seconds.

Q: What is the NetCDF time convention?

Typically **hours or days since 1900-01-01** (CF conventions), stored as float. Convert with `time + ref_date`.

MATLAB `datenum` counts days since `0000-01-00` (Jan 0, year 0), producing values like 740,000+ for modern dates. NetCDF times are typically days/hours since a reference (often 1900-01-01), and Mathematica `AbsoluteTime` counts seconds since 1900-01-01.

This converter renders your date-time in each scientific representation so you can decode `.mat` files, NetCDF variables and Mathematica exports.

Timezone:

Enter a date-time above to see the conversion results.

MATLAB datenum Converter Quick Reference

Format	Pattern / Description	Example 1	Example 2
MATLAB datenum	Days since 0000-01-00	740207.60417	739983.00000
NetCDF Time	Days since 1900	days since 1900-01-01 (46245.6042)	days since 1900-01-01 (46021.0000)
Mathematica Absolute	Seconds since 1900	3995620200	3976214400

* Examples are rendered in UTC for the fixed sample instants above.

When to Use MATLAB datenum

MATLAB data import

Decode `datenum` columns exported from MATLAB when moving data to other tools.

NetCDF climate & sensor data

NetCDF time variables store offsets from a reference date; convert them to wall-clock for analysis.

Mathematica time series

Convert `AbsoluteTime` values from Mathematica exports to readable dates.

Frequently Asked Questions

What is MATLAB datenum?

A count of days since Jan 0, 0000 (i.e. 1 = 0000-01-01). Modern dates are ~740,000. The fractional part is time of day.

What is Mathematica AbsoluteTime?

Seconds since 1900-01-01 00:00:00, as an integer. 2026-08-13 ≈ 3,996,000,000 seconds.

What is the NetCDF time convention?

Typically hours or days since 1900-01-01 (CF conventions), stored as float. Convert with `time + ref_date`.

Is MATLAB datenum the same as Excel serial?

No — Excel counts from 1899-12-30 (serial ~45,000 for 2023), MATLAB from year 0 (~739,000). They differ by ~694,000 days.

Related Time Format Converters

Excel Serial Date Converter

Convert dates to Excel serial numbers (45251.61) and back. Supports 1900 and 1904 date systems. Free converter for spreadsheet and CSV work.

Julian Date Converter (JD & MJD)

Convert calendar dates to Julian Date (JD) and Modified Julian Date (MJD). Continuous day count for astronomy, aerospace and date arithmetic. Free converter.

Unix Timestamp Converter (Epoch Time)

Free Unix timestamp converter. Convert epoch seconds, milliseconds, microseconds and nanoseconds to human-readable dates instantly. UTC & local time, one click copy.

All Format Guides

Unix Timestamp ISO 8601 ISO Week Date ISO Ordinal Date Military Time Decimal Time RFC 2822 RFC 3339 SQL Datetime Julian Date HTTP Date Excel Serial Date GPS Time UTC Time Cron Expression

Browse all 50 format guides →

Need to Convert Between All Formats?

Use the main Time Format Converter for instant conversion across 100+ formats — epoch, ISO 8601, RFC 3339, SQL datetime, military time and more in one click.

Open Time Format Converter