Failed to retrieve GVO observations when dealing when using forecast timestep of 1 month

Currently, observations are detected within an interval t +- dft / 2. However, GVO times aren't rounded (e.g. 2000.08333, end of January). Two possibilities :

• Measures are done at the end of January
• Decimal part exists because of a bad conversion of the timestamp into years

Until we have an answer to this question, it is sufficient, given that dtf >= 1 month, that we put t +- 0.1 instead of dtf / 2 as a temporary fix.