The Calendar of Imladris
The Elves of Rivendell used a solar calendar much like our own. A year was nominally 365 days long, with three extra days added every twelfth year to keep the calendar aligned with the seasons. The year began at the Spring equinox, and was divided into six seasons:
Each season was further divided into six-day weeks:
|Orgaladhad||Day of the Two Trees|
|Ormenel||Day of the Heavens|
|Orbelain||Day of the Valar|
Conveniently, each season was a multiple of 6 days long, so seasons always began on Orgilion and ended on Orbelain.
The seasons only total to 360 days, so in every year there were a few days not considered part of any season. These were:
Last Day, following Echuir
First Day, preceding Ethuil
- Three Enderi or
Middle Days(the Quenya name; it's unknown what these might have been called in Sindarin) at the Autumn equinox, following Iavas. In every twelfth year, the Enderi were doubled to six days.
The Unix Epoch
The Reckoning of Imladris has, regrettably, not been maintained since the end of the Third Age, and so while we can still use the calendar to determine the date based on the seasons, it's unclear how years should be counted. I've arbitrarily chosen the Unix Epoch of January 1, 1970—a significant date for programmers—as the date at which to start counting.
Actually, that's not quite right, because the calendar of Imladris doesn't begin on January 1st. So March 22, 1970 is the start of Year 1 of the Unix Era, abbreviated 1 U.E.