Consistency check for date time pattern if using InfluxDB

[ckittl]

When querying InfluxDB, results contain a time stamp in RFC 3339 format. (cf. InfluxDB doc). However, currently, the factories being used for parsing, may rely on a different kind of format.

A similar issue arises with other sources, that might query based upon a notion of time. I would suggest to make the factories' time stamp pattern accessible from outside, so that either consistency checks are possible or one can use the factory's pattern for other purposes.