Sundays child  math puzzle
Recently, somebody told: "My grandfather was born on the first sunday of the year. His seventh birthday was also on a sunday!" In which year was this grandfather born?
Explanation
Usually a date shifts by one day every year. So if for example 29 march is on a sunday, next year it will be on a monday. But if the next year is a leapyear, the date shifts by two days, in the example 29 march becomes a tuesday.
In seven years we expect at least one leapyear so after seven years you never can get the same day for the same date. But 1900 was not a leapyear (like all other years which are divisible by 100, except for the ones which are divisible by 400). Hence grandfather was born around 1900, in 1897 (because here the 7year period is possible). More exactly he was born on January 3, 1897.
In seven years we expect at least one leapyear so after seven years you never can get the same day for the same date. But 1900 was not a leapyear (like all other years which are divisible by 100, except for the ones which are divisible by 400). Hence grandfather was born around 1900, in 1897 (because here the 7year period is possible). More exactly he was born on January 3, 1897.
