The canonical Lojban calendric system(s) are discussed in http://www.opoudjis.net/lojbanbrochure/lessons/less5days.html ; they are number-based. (January = pavmast., Sunday = nondjed.)
The chief holiday is Logfest, held on a weekend in July on various dates.
There are exactly twelve color gismu (see: http://members.tripod.co.uk/lojbanlinks/skari.html), & various attempts to match up the regular months of the year have been proposed. E.g.
in the beginners' stuff in this order:
blabi, grusi, xekri, xunre, crino, blanu, pelxu, cicna,
nukni, zirpu, bunre, narju
le'i mastycme
la labmast. la ri'ormast. la nukmast.
la rusymast. la blamast. la zirmast.
la xekmast. la pelmast. la burmast.
la xunmast. la cicnymast. la najymast.
The days of the week have been correlated to metals, & other sets of mnemonic or mythological names... E.g.
we can translate our existing weekdays back into
planets & then into the lojbanic names for their traditional
metal correspondences:
le'i jefcme
monday= la rijdei
tuesday= la tirdei
wednesday= la magdei
thursday= la tincydei
friday= la tukydei
saturday= la nisydei
sunday= la slodei
the traditional assignment of colors to planets gives:
monday white = la labdei
tuesday red = la xundei
wednesday gray = la rusydei
thursday blue = la bladei
friday green = la ri'ordei
saturday black = la xekydei
sunday yellow = la peldei
Another proposal uses the signs of the zodiac for months and the Japanese and Korean names for the days of the week. See Dates and Times in the Phrasebook.
Other proposals, some of them rather extensive, can be found be clicking the "discuss" tab below.