The Typicon has no instruction to ‘make up’ for a missed fasting day, such as Wednesday or Friday, by fasting on another day.
But, despite the absence of such a rule, this practice is not at all reprehensible; quite on the contrary it is rather pious. If we look into the history of the Apostolic (St Peter’s) fast, we will see that in ancient times it did not exist as an independent fast for many days. In the early Christian essay titled the Apostolic Tradition, usually attributed to the holy martyr Hippolytus of Rome (+ 235), this fast is presented as a kind of “compensation” where those unable to fast during Great Lent had to “make up” for it after the holidays.
In a similar way, if due to certain circumstances we were unable to keep fast, for example on Wednesday or Friday, it would be useful and pious to fast on some other day. The only exception may be Sunday, when fasting is strictly prohibited by church canons.
Andrey Muzolf, lecturer at the Kiev Theological Academy
Translated by The Catalogue of Good Deeds
Source: https://pravlife.org/ru/content/esli-propustil-postnyy-den-mozhno-li-popostitsya-v-drugoy
