An almanac was a publication of calendars which could be used to track meteorological or agricultural information over time.
In 2376, when the USS Voyager became trapped in orbit of a planet where time was accelerated, The Doctor was sent to the surface to retrieve information. He then returned, having committed to memory meteorological records and seismic analyses for three hundred years, though some of the older records were imprecise almanacs. (VOY: "Blink of an Eye")
In approximately 3074, an artifact buried nine meters beneath the ruins at Kesef on the Kyrian and Vaskan homeworld was uncovered by a Kyrian research team. The artifact was a data storage device which came from Voyager. Quarren speculated that the active data could contain Captain Kathryn Janeway's personal almanac. (VOY: "Living Witness")