Mainframe Date Converter (COBOL, RPG, MUMPS)

Q: What is MUMPS $H?

`$HOROLOG` = **days since 1840-12-31** plus seconds since midnight, comma-separated: `67823,52200`. Modern dates ≈ 67,000+ days.

Q: What is OpenVMS binary time?

A 64-bit count of **100ns since 1858-11-17 00:00 UTC** (the Modified Julian Date epoch). Values ≈ 5.3×10¹⁶ for 2026.

Q: What is the RPG Julian date?

**`YYDDD`** (2-digit year + day of year) or `*JULIAN` in newer RPG — e.g. `26225` for 2026 day 225.

Q: How do COBOL dates look?

Often **`YYYYMMDD` as PIC 9(8)** (display or COMP-3 packed), or Julian `YYYYDDD`. The exact picture clause varies by shop.

Legacy platforms encode dates their own way: COBOL (various PIC 9 formats and Comp-3), RPG (Julian or *ISO), MUMPS `$H` (days since 1840-12-31 + seconds), and OpenVMS (100ns since 1858-11-17).

This converter renders your date-time in each mainframe representation so you can read dump files, migrate legacy data, and build conversion jobs.

Timezone:

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

Mainframe Date Converter (COBOL, RPG, MUMPS) Quick Reference

Format	Pattern / Description	Example 1	Example 2
COBOL (Comp-3)	CYYDDD (Year since 1900)	260813	260101
IBM RPG / AS400	CYYMMDD	1260813	1260101
MUMPS $H	Days,Seconds	67795,52200	67571,0
OpenVMS Time	DD-MON-YYYY HH:mm:ss.cc	13-AUG-2026 14:30:00.00	01-JAN-2026 00:00:00.00

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

When to Use Mainframe Date (COBOL, RPG, MUMPS)

Legacy data migration

Decode MUMPS $H and OpenVMS timestamps when migrating EHR and finance systems to modern platforms.

COBOL modernization

Generate expected COBOL numeric date values for test cases during refactoring.

Dump & log analysis

Interpret RPG Julian and OpenVMS binary times from mainframe logs and dumps.

Frequently Asked Questions

What is MUMPS $H?

`$HOROLOG` = days since 1840-12-31 plus seconds since midnight, comma-separated: `67823,52200`. Modern dates ≈ 67,000+ days.

What is OpenVMS binary time?

A 64-bit count of 100ns since 1858-11-17 00:00 UTC (the Modified Julian Date epoch). Values ≈ 5.3×10¹⁶ for 2026.

What is the RPG Julian date?

`YYDDD` (2-digit year + day of year) or `*JULIAN` in newer RPG — e.g. `26225` for 2026 day 225.

How do COBOL dates look?

Often `YYYYMMDD` as PIC 9(8) (display or COMP-3 packed), or Julian `YYYYDDD`. The exact picture clause varies by shop.

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