There's also a noticeable drop on the 13th of every month - if people have a choice in the date, some are opting not to do it on an unlucky day.
It could also be elective surgery numbers in general, but the February 29th being the lowest rank makes me think birthdates.

Most common birthdays. February 29 ranks lowest, followed by Christmas and Boxing Day. There's a bump a week before Christmas - people getting their elective C section and inductions in, and a big jump in the first week of January when hospitals reopen for elective procedures.

I am going on tour. Maybe I will be near you, and if so maybe you would like to hear me talk about Lane Holland, the weirdest type of murder I've ever heard of and why writing VANISH made me start seeing ghosts on my farm
www.hachette.com.au/news/shelley...

Amazing! Congratulations

The buck is Sugar, and it's taking all my willpower not to suggest she name the remaining two Honey and Ice Tea

Thank you! I'm putting the finishing touches on book three now, it will be out at the end of April