GILH 96: ... First Vespers ... may not be celebrated until after the Mass of the previous day or the Saturday.
And changing the liturgical day would take more than this :-Code of Canon Law 1917: Can. 202 з1. In law, a day is understood as a period consisting of 24 continuous hours and begins at midnight unless other provision is expressly made; ... .
Cum hæc nostra ætate 1955 :
d) Other changes
11. First Vespers (whether entire, or a capitulo, or by way of
commemoration) pertain only to feasts of the first and second class
and Sundays.
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