noun
Edo–early Meiji non-working day on dates with 1 or 6
Historical term for a regular holiday observed from the Edo period into the early Meiji era. It fell on the 1st, 11th, 16th, 21st, and 26th of each month—days whose dates, when written in kanji numerals, contain the characters 一 (1) or 六 (6).
江戸時代、商家では一六日を休みとすることが多かった。
During the Edo period, merchant houses often took 一六日 as a day off.
一六日は、月に五回ほど巡ってくる休日だった。
一六日 was a holiday that came around about five times a month.