How did Grandma Jeanetta keep track of their birthdays?

Did you know that the eldest daughter of George and Jeanetta Menzies, Annie Isabella Menzies, married Ernest Woodley Warner in 1885 and bore him 10 children between then and 1907. This 10 in 19 years!

Her sister Jessie McKindley Menzies married Thomas Aubrey in 1890 and bore him 5 children up to 1904. This is 5 in 14 years.

This was not so odd for the times except that the sisters were giving birth at the same time. Their mother, Jeanetta, had her last baby, Maggie Grace, in 1883 and then her eldest daughter, Annie, had her first, ‘Netta Anne Warner in 1887, her second, Earnest Warner, in 1889 and her third George Warner in 1891.

Jessie had her first, Will Aubrey in 1891 and her second, Annie Aubrey, in 1892. It was Annie’s turn next with Arthur in 1893. They both had babies in 1894, Annie had Ethel (Dot) and Jessie had Tom.

Annie was next with Annie in 1896 followed by Jessie with Jessie in 1897. Annie followed with Ruby in 1898 and things were relatively quiet till Annie gave birth to Willie in 1903, Kathleen in 1905 and finally Jessie in 1907.

Her sister Jessie had only one more baby and that was Robert in 1904, sadly after his father was tragically killed in an accident.

A total of 15 births in 19 years. How ever did Grandma Jeanetta keep track of their birthdays?