Dealing with dateTime for prepbufr files

[nicholasesposito]

We were talking about the emctank in today's meeting. For the project where we retrieve 3 months worth of data from specific data types/files.

Something that needs to be considered is the way prepbufr deals with dates. The only mention of time in mnemonics is "DHR" which is the "cycle time minus the obs time". For example, if the file is a 00z file and DHR is -2.5, then the data is from the previous day at 2130Z. If we're making a container full of all this data, we need to have a way to have the right time for each of the 4 data files per day.

@rmclaren