The period code describes the time span covered by the time series contained in the file. The period code is constructed by a number and a period code tag.
The period code should be an approximate indicator of the time coverage of the file and thus may divert someehow from the exat time coverage (e.g. 364 days may be reported asi 1y)
<int><period code tag>
List of valid period code tags:
||6 months, half a year
Period code: 1y