An interesting fact for you - promulgation doesn't have to be on Tynwald Day, in fact promulgation used to take place when necessary. Read the Legislation Act 2015 from page 9 onwards and you'll notice that nowhere in it does it state that they have to be promulgated on Tynwald Day.
The below is taken from Peter Edge's book on Manx Public Law:
"A consideration of promulgation between 1700 and 1800 indicates that Tynwald Day was preferred but not essential. Between these dates two Acts were promulgated in February; three in April; one in May; thirty-eight in June; seventeen in July; one in August; twenty two in September, seventeen of which were promulgated at the same time; three in October; and two in November. Taking into account the postponement of any Tynwald day which fell on a Sunday, and the adoption of the Gregorian Calendar during this period, of the eighty-nine Acts promulgated during this period, forty-six were promulgated on Tynwald Day."
I am sure I have read of an example in the 20th century as well.