Some ancient calendars
The indication of the Julian date of the first month in each calendar is only an approximate guide. All of these calendars varied, some of them very widely, from their supposed starting point in the solar year. For more information about each of the calendars, see the detailed chronological tables that have been compiled by Chris Bennett.
Babylonian (Jewish) calendar
Nisanu (Nisan) = April
Aiaru (Iyyar)
Simanu (Sivan)
Duzu (Tammuz)
Abu (Ab)
Ululu (Elul)
Tashritu (Tishri)
Arasamnu (Marheshvan)
Kislimu (Kislev)
Tebetu (Tebeth)
Shabatu (Shebat)
Addaru (Adar)
To convert Babylonian dates into Julian dates, see the Babylonian Calendar Converter.
Egyptian calendar
Thoth = first month of akhet season
Phaophi
Hathyr
Choiak (or Choiach)
Tybi = first month of peret season
Mecheir
Phamenoth
Pharmouthi
Pachon = first month of shemu season
Pauni
Epeiph
Mesore
To convert Egyptian dates into Julian dates, see the Date Converter for Ancient Egypt.
Greek (Athenian) calendar
Hecatombaeon = July/August
Metageitnion
Boedromion
Pyanepsion
Maemacterion
Poseideon
Gamelion
Anthesterion
Elaphebolion
Munychion
Thargelion
Scirophorion
Macedonian calendar
Dius = October
Apellaeus
Audnaeus
Peritius
Dystrus
Xandicus
Artemisius
Daesius
Panemus
Loius
Gorpiaeus
Hyperberetaeus
Roman (pre-Julian) calendar
Januarius (29 days)
Februarius (28 days)
Martius (31 days)
Aprilis (29 days)
Maius (31 days)
Junius (29 days)
Quintilis (31 days)
Sextilis (29 days)
September (29 days)
October (31 days)
November (29 days)
December (29 days)
https://www.instonebrewer.com/TyndaleSites/Egypt/ptolemies/chron/roman/chron_rom_cal.htm
To convert Roman dates into Julian dates, see the Roman Calendar Conversion Table, with Guidance.
Attalus' home page