This long-standing tradition was here long before Jesus appeared before Pontius Pilate
Actually that is not true. We ware fortunate enough to have written records of how the dates of Easter were chosen as as part of the creation of the Holy Roman Catholic Church during the
Council of Nicaea in 325, as a replacement for the Hebrew celebration of passover. Early Christians had already adopted the practice of celebrating Easter during Passover on the basis that the Last Supper was itself held on passover - again there are ample written records of this practice thanks to considerable disagreement on how the dates of both Easter and Passover should be calculated. Many non English languages use the same (or very similar) word for Passover and Easter.
So nothing to do with paganism I am afraid.
We actually don't know that pagans even celebrated the spring equinox as there was no written records prior to Julius Caesar and the only reliable archaeological evidence for possible prehistoric celebrations is at the solstices (and even that evidence dates to several thousand years before Roman times, which means that we cannot be sure that such traditions had not died out by that time).
The belief in a pagan celebration of the equinox is probably a Victorian fantasy most likely invented by
Margaret Murray who along with
Gerald Gardener made much of what we believe to be our pagan past. These folks and their adherents may well have created a pagan calendar of celebrations to fit the Christian calendar rather than the converse as is often claimed today.
Even the supposed name of the pagan goddess of Easter - Ēostre - is from a language - Old English - which did not exist until around 600AD, about 400 years
after people started to celebrate Easter.
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Anyhoo back on topic.
When I was young (1970s) the local early closing day was Tuesday and may local retailers closed at 1PM (indeed in those days most still closed between 1PM and 2PM for Lunch on weekdays - most stayed open through lunch on a Saturday).
However by the time I was in Secondary School (1981) this tradition was dying out, starting first with the larger stores it spread quickly to all, and by the time I left School it was something of a memory, and Sunday opening was becoming the norm.
In those days Scotland did not take the Easter Holidays (or any of the
English bank holidays, instead taking a local early Spring holiday the dates of which were set individually by local authorities - in my back yard Glasgow happened to set theirs to coincide with Easter Monday, while Paisley set theirs to be the week after. In my hometown of Barrhead the Post office used to follow the Glasgow Holidays whilst most other businesses followed Paisley.
As well as the locally set holidays that were once well observed Scotland also had it's own national Bank Holidays which were largely unobserved (unless the happened to fall on a local holiday) even by banks.
Widespread observance of Good Friday and Easter Monday as holidays is relatively recent up here (in the West of Scotland the local government reorganization prompted many of the new councils to align their holidays with Glasgow's - which were already aligned with the English holidays), ironically this practice has developed during a time where observing the other public holidays was on the wane.
Today (at least in Edinburgh and its surroundings) Easter seems to be the only public holiday that is sufficiently observed to cause a noticeable reduction in road and public transport traffic - even though it is not officially a holiday (The official Edinburgh holiday was April 14th).