Possible to Schedule a Cron Job for Specific Day of Every Month on Google App Engine?

Question

Is it possible to schedule a cron job on google app engine to run on the 27th day of every month?

Background

Looking at their 开发者_如何学运维syntax here, it appears doing that is too specific, but I wanted to see if anyone here managed to do it somehow.

Interestingly enough, this works:

 1st day of jan,feb,mar,apr,may,jun,jul,aug,sep,oct,nov,dec 00:00

but this doesn't:

27th day of jan,feb,mar,apr,may,jun,jul,aug,sep,oct,nov,dec 00:00

All I did was change the day number (ordinal), but it seems that if the ordinal is greater than 5, you get an exception (Parent module 'antlr3' not loaded). I assume this is because the parser is mistakenly letting the "1st day" get through thinking it means "weekday of the month" or something like that.

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Keep it simple, stupid ! ;)

27 of month 9:40

Tested and worked.

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UPDATE: This answer is obsolete; see new accepted answer.

It appears this currently is not possible, though I still don't know for certain.

Thus, my work around is to setup a cronjob to run every day, and have the method it's calling return early if it's not the 27th. ~29 extra requests per month isn't that bad, right?