The date has the following format[19](compatible and with the same semantics of RFC 2822 and RFC 5322):
day-of-week, dd month yyyy hh:mm:ss +zzzz
where:
day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
dd is a one- or two-digit day of the month (01-31)
month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec
yyyy is the four-digit year (e.g. 2010)
hh is the two-digit hour (00-23)
mm is the two-digit minutes (00-59)
ss is the two-digit seconds (00-60)
+zzzz or -zzzz is the the time zone offset from Coordinated Universal Time (UTC). "+" indicates that the time is ahead of (i.e., east of) UTC and "-" indicates that the time is behind (i.e., west of) UTC. The first two digits indicate the hour difference from UTC and the last two digits indicate the number of additional minutes difference from UTC. The last two digits must be in the range 00-59.
apt in Ubuntu Xenial now complains about the date format in the release file.
It appears as though this repository is abandoned. I've forked this repository (https://github.com/mschwager/prm) and included the commit that fixes this issue.
According to RepositoryFormat and the Debian Policy Manual 4.4, the authoritative source on the date format:
apt in Ubuntu Xenial now complains about the date format in the release file.