One of my favourite programming inconveniences and frequent source of bugs is shared by Java and Perl, so it is probably inherited from C and cannot be changed in order not to break old and fearsome legacy code.

Java

java.util.Calendar.set

public final void set(int year,
                      int month,
                      int date)

Sets the values for the fields year, month, and date. Previous values of other fields are retained. If this is not desired, call clear first.

Parameters:

year - the value used to set the YEAR time field.

month - the value used to set the MONTH time field. Month value is 0-based. e.g., 0 for January.

date - the value used to set the DATE time field.

Perl

localtime EXPR

Converts a time as returned by the time function to a 9-element list with the time analyzed for the local time zone. Typically used as follows:

# 0 1 2 3 4 5 6 7 8 ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime(time);

All list elements are numeric, and come straight out of the C `struct tm'. $sec, $min, and $hour are the seconds, minutes, and hours of the specified time. $mday is the day of the month, and $mon is the month itself, in the range 0..11 with 0 indicating January and 11 indicating December. $year is the number of years since 1900. That is, $year is 123 in year 2023. $wday is the day of the week, with 0 indicating Sunday and 3 indicating Wednesday. $yday is the day of the year, in the range 0..364 (or 0..365 in leap years.) $isdst is true if the specified time occurs during daylight savings time, false otherwise.