On May 21, Orthodox and Catholic Christians celebrate the day of Saints Constantine and Helen
The period in which they ruled was known as the golden age, because of them Christianity was allowed and bloody sacrifices were forbidden,
And Sunday was established as a day of rest in the Roman Empire

In order to realize all this,
we will briefly unravel the thread of history in order to refresh in our minds and hearts the events that took place then.
The cruelest persecution of the Church was under the Emperor Deocletian,
in 303 he proclaimed the harshest edict of persecution of Christians in the entire Roman Empire,
by his order began throughout the Greco-Roman world the action against Christians by demolishing the Churches,
burning and defilement of books and holy objects,In all parts of the empire the blood of the Christians was shed like water and no place was to be found,
to hide the believers of Christ, yet as the tortures intensified, the Christians overcame the oppressors by faith and patience in suffering.

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The emperor Diocletian himself, terrified by the massacre caused by him and his ambition,
worked by great mental disorders and terrified by bad omens, on May 1, 305,
abdicated from the throne in front of the army.
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He left Gabriel as his successor in the east and St. Constantine's father in the west
Gabriel continues the persecution against Christians this makes St. Constantine who is at Gabriel's court to go to his father in Britain
In the same year, 305, when his father died, the army chose Saint Constantine as emperor,
having dominion over Britain, Gaul and Spain, together with Maxentius, who ruled in Italy and North Africa,
Maxentius was a tyrannical emperor who continued to oppress Christians and started a war against Constantine.
Saint Constantine, being in front of Maxentius' army 3 times bigger than his army, resorted to God, whom his father called God of the Sun.

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https://ro.wikipedia.org/wiki/Sfin%C8%9Bii_%C3%8Emp%C4%83ra%C8%9Bi_Constantin_%C8%99i_Elena
(google translate)