I decided some time ago to take over the development of at daemon.

Here is a new release of at v3.1.17

From the Changelog:

at 3.1.17 (2015-08-31):

  Jose M Calhariz:
        at.1.in: Document behaviour when using past time, thanks Kelly Price (Closes: #639900).
        Makefile.in: On distclean remove at.allow.5, auto generated file.