From Hydrogenaudio Knowledgebase
This is how dates and times are to be represented in the APEv2 tagging system:
 Date and Time Format
Date and Time Formats are used to address time points not related with the playback. Usually longer time periods (1 . . . 500 years) with less accuracy (1 day . . . 1 year) are addressed.
- It uses ISO 8601 as time format to overcome ambiguous national formats.
- Format is "big endian" text format like the normal arabic numbers. Left digits have a higher weight than right digits.
- So the meaning is YYYY-MM-DD hh:mm:ss, where YYYY is the year, MM the month, DD the day, hh the hour since midnight, mm the minutes and ss the seconds.
- Year is four digits, other items are two digits long.
- Year, month and day are hyphen separated, hour, minute and second with a colon.
- You can remove right side number for reduced precision representation.
- To address a special week, the format is YYYY-Www, where YYYY is the year and ww is the week. Week #1 is the first week with it's wednesday in the new year. Weeks #1 until #53 are possible.
- 1999-08-11 12:34
- 1999-08-11 12:34:56