Foobar2000:Encouraged Tag Standards

LAST_PLAYED

Basics:

the tag-fieldname used for storing info when a song was played the last time is "LAST_PLAYED"
tag contains date and time in the following format at the beginning: "YYYY-MM-DD HH:MM:SS" (with 24hours-format)
additional info may be appended after the above info

Reasons for deciding on this format:

the APE-dateformat (derived from ISO) is internationally neutral
sortable
easily readable and recognizable
format can be verified with TAGZ
can be included in formatting-strings without reformatting it (pro for amateur tagz-coders)
choosing a new fieldname avoids confusion with the existing ambigious play_date tag
tag-fieldname is easy to understand/recognize/remember and short enough to type in manually

Code snippets:

// verify tag-format (we check the pos. of the first dash and ":")
// using $len for verification is strongly unrecommended!
$if(
$and($strcmp($strstr(%last_played%,-),5),$strcmp($strstr(%last_played%,:),14))
,$puts(last_played_is_valid,1)
)

// disassemble the timestamp for later reformatting or calcuations
$puts(last_played_year,$substr(%last_played%,1,4))
$puts(last_played_month,$substr(%last_played%,6,7))
$puts(last_played_day,$substr(%last_played%,9,10))
$puts(last_played_hour,$substr(%last_played%,12,13))
$puts(last_played_min,$substr(%last_played%,15,16))
$puts(last_played_sec,$substr(%last_played%,18,19))

// display only the date of last_played (without reformatting)
$left(%last_played%,10)

// display only the time of last_played (without reformatting)
// the use of $right is strongly unrecommended!
$substr(%last_played%,12,19)

PLAY_DATE

Obsolete artifact of foo_playcount. Default format was DDMMYY. See LAST_PLAYED.

PLAY_TIME

Obsolete artifact of foo_playcount. Default format was HHMMSS (24hr). See LAST_PLAYED.

ALBUM ARTIST

A tag indicating the tagged album's artist. Use "Various Artists" or "VA" for multi-artist albums for clarity. This is the preferred method of handling compilations, DJ mixes, and the like. VARIOUS=1 and similar hacks are neither clear, concise, nor informative. ALBUM ARTIST handles all of these issues gracefully.