The problem of calendar reform

Abstract EN

The Gregorian reforms were implemented in the year AD 1582 to keep the Julian calendaric system in coincidence with the tropical year.

However, these reforms were also not without approximations, so errors have continued to accumulate since then.

Intercalation (to add a certain number of days after a fixed period) is employed to overcome such errors.

In the Julian and Gregorian calendars it is accepted to increase a day in the month of February.

In the Julian system every year divisible by 4 is considered as a leap year and the month of February in that year has 29 days instead of the usual 28 days.

In the Gregorian system the rule is the same except that a centesimal year is considered to be a leap year only if it is divisible by 400.

This communication aims at clarifying various confusions arising as a result of these intercalations.

Also, there exist well qualified modifications (which suggest a rectification of the leap year rule itself) in the Gregorian system enabling it to remain serviceable for still longer periods.

We have performed a verification of one such suggestion.

We have also reviewed the calendaric system of Umar Khayyam for its potential as an alternative of the Gregorian system.

However, its adoption is a matter for consideration by the IAU.