Sounds like someone’s had a rough twenty months.

Remember that a year on Mars lasts two Earth years, so Maida’s mom is used to counting up to 23 months before switching units of time. Also this means Maida has still only had the one birthday on Earth, despite living there for nearly two (Earth) years. Maida, meanwhile, has switched over to keeping track of her age in two modes simultaneously. See back just a few pages ago at the start of this chapter.