Jane was born on first Sunday of the year in 1897. Checking a calendar, that was on Jan 3, 1897. So she would be 25 on Jan 3, 1922.
Ben was born on the 'same day of the year' in 1918. The 'same day of the year' could mean Jan 3, 1918 or could mean the first Sunday of year, 1918, which would have been Jan 6, 1918.
So Ben would be 5 on either Jan 3 or Jan 6, 1923.
The years still don't seem to work out for Jane to be 5 times as old as Ben. Unless Ben was born early in the day on Jan 3 and Jane was born late in the day on Jan 3, so technically Jane would still be 25 at the time Ben was 5 on Jan 3, 1923.