Adult calendar calculators in a psychiatric OPD: a report of two cases and comparative analysis of abilities.

Two men in a psychiatric clinic could name the day of the week for any date you gave them. The doctor timed their answers to see how fast they were.

He tested many dates and watched how long each answer took. He wanted to know if the men were using the same trick or two different tricks.

Both men were faster when the date was close to the year 1900 and slower for dates far away. Their speed changed in the same pattern, like two people using the same map.

The pattern fit a simple calendar rule, not random memory. This hints that calendar savants share one basic method.

Chiviacowsky et al. (2013) also watched one patient for five years. They showed that anxiety can hide autism signs, so you must keep testing. Both papers warn: look past the first answer you see.

Ten Hoopen et al. (2025) found that small things—like a child moving too much—can nudge ADOS-2 scores. Allen (1981) adds another small thing: the date you pick can nudge reaction time. Both tell us to control the little details during testing.

de Bildt et al. (2011) made ADOS scores line up across age and module. Allen (1981) did the same kind of lining-up, but for speed instead of score. Each paper shows how to make numbers fair to compare.

If you test a savant skill, pick your probe dates with care. Stay close to the client’s anchor year to keep times short and steady. This gives cleaner data and helps you see true ability, not test noise.