An Eastern tradition attributes a duration of 70 years to the life of the Virgin Mary. This tradition divides the Virgin Mary's life into ten septenaries (seven times ten years).
These ten seven-year periods can in turn be subdivided into 20 half-seven-year periods, or 3 and a half years: a duration often found in the Bible[1].
The birth of the Virgin Mary in 19 BC occurred in the year Herod the Great decided to rebuild the Second Temple (cf. Jn 2:20), an image of the construction of the true Temple represented by the Virgin Mary. Between this date and the Annunciation (between 19 BC and 5 BC), the Virgin Mary spent her childhood first with Anne and Joachim - until the age of three and a half, according to Tradition - and then in the Temple.
Between 5 BC and 30 BC, there are five seven-year periods, two of which correspond to the childhood of Jesus (born in 4 BC), first in Egypt, then in Nazareth, until his Bar Mitzvah and recovery of Jesus in the Temple, then three seven-year periods of hidden life in Nazareth, with Joseph and then without him, after his death, the last half-seven-year period corresponding to the three and a half years of Jesus' public life.
Between the year 30 and 15 August 51, the date of Mary's departure for heaven according to one tradition, there are three septenaries, the first corresponding to the Pentecost cycle, the second to the departure for Ephesus where John and Mary remained hidden, leading a contemplative life and deepening their understanding of the mystery of God for three and a half years because of persecution, before finally returning to Jerusalem, where Mary ended her life, having passed on to Saint Luke the accounts of her childhood, the parables of Mercy and the Passion.
Tosum up, here are the 10 Seven Years of Mary's life:
[1] cf . 11,2 or Ap. 13,5: "42 months" or Ap. 11,3 or Ap. 12,6 : "1.260 days" or Ap. 12,14 : "one time, two times and half a time").
on the life of the Virgin Maryin the Marian Encyclopaedia
L’équipe de MDN.