I always keep pretty tight track of the passing of time and days in my stories.  In some, like Senta and the Steel Dragon, that got pretty complicated because I also created my own calendar with new months.

When I started writing Astrid, in 2010, I began using a 2012 calendar and kept track of the events in the story.

Astrid Maxxim and her Amazing Hoverbike takes place from March 3 to April 7.

Astrid Maxxim and her Undersea Dome takes place from April 22 to May 26.

So there are just a few weeks of character time between each story, even though for me, about a year and half has passed.