last December; end of last year
Literary or old-fashioned term for the end of the previous year, especially the last month. In modern Japanese, 去年の十二月 or 昨年末 are far more common.
In this season of last December, I trust you are all doing well. (A formal, old-fashioned seasonal greeting.)
Last December, this area was hit by record-breaking heavy snow. (Literary style.)
A literary Sino-Japanese compound of 旧, “previous,” and 臘, the twelfth lunar month or year-end season, hence “last December” or “the end of last year.”