Q 01/05

Which Roman leader proposed the calendar reform of 46 BC that replaced the earlier Roman calendar?

A) Pompey Magnus

B) Augustus Caesar

C) Julius Caesar

D) Mark Antony

Answer · why

C) Julius Caesar

The reform took effect on 1 January 45 BC and gave the year 365.25 days on average.

Q 02/05

Which Alexandrian astronomer is considered the principal designer of the Julian calendar?

A) Sosigenes

B) Ptolemy

C) Eratosthenes

D) Hipparchus

Answer · why

A) Sosigenes

Pliny credits him; he may also have written the astronomical almanac Caesar published to help people use the new calendar.

Q 03/05

Which pope issued the 1582 bull Inter gravissimas that reformed the calendar?

A) Clement VII

B) Paul III

C) Sixtus V

D) Gregory XIII

Answer · why

D) Gregory XIII

The bull was dated 24 February 1582 and the new calendar took effect that October.

Q 04/05

How many days were skipped in October 1582 when the reformed calendar took effect?

A) 13

B) 10

C) 11

D) 12

Answer · why

B) 10

Thursday 4 October 1582 was followed directly by Friday 15 October, and the weekday cycle was left unbroken.

Q 05/05

Which Calabrian doctor's proposal, after modification, became the basis of the 1582 calendar reform?

A) Aloysius Lilius

B) Tycho Brahe

C) Erasmus Reinhold

D) Nicolaus Copernicus

Answer · why

A) Aloysius Lilius

He died in 1576, so his brother Antonio presented the plan in Rome; the 'Lilian date' in computing counts days from 15 October 1582 in his honour.