I have noted that women with Borderline Personality Disorder are strangely locked in the circular time of the yearly calendar, especially with regards to those who they have poor boundaries with - the anniversary of their mother's or sister's death or birthday, especially. As they are often very pet and animal focused (a common volunteer job we can generate excitement for is work at an animal shelter), even the anniversary of a pet's death can set them off.
I have speculatively attributed this to some odd time-sense or faulty time perception. But in commenting on Staffan's new post today, it occurred to me that the cause might be more general. They are very easily triggered into emotion chaos by events associated with past trauma. The overlap of BPD and PTSD is significant. The events of the calendar may simply be triggers of past trauma, no more significant than a smell or an associated song.