Yordan Valchev noticed that in the Bulgarian calendar the odd dates where the number of the day is the same as the number of the month

First Half of the Year Odd
1^-st day of the First Month (1.I), 3^-rd day of the Third Month (3.III) and 5^-th day of the Fifth Month (5.V) i n the Bulgarian calendar, are always on the first day of the week,

Second Half of the Year Odd
7^-th of the Seventh Month (7.VII), 9^-th day of the Ninth Month (9.IX) and 11^-th day of the Eleventh Month (11.XI) are always on the last (7^-th) day of the week.

He accepts these days - the first (according to him Sunday) and the last (Saturday) for "male" official holidays, on which important decisions have been made for the state

On the other hand, even dates where the number of the day and the number of the month are the same: 2.II, 4.IV, 6.VI, 8.VIII, 10.X and 12.XII are always on workdays (other than the first and last day of the week) and were conventionally called "female" holidays related to the household or family.