Improve creation_time and origin_time check

Currently the used regex is [0-9]{4}-[0-9]{2}-[0-9]{2} [0-9]{2}:[0-9]{2}:[0-9]{2} +00 This accepts 9999-99-99 99:99:99 +00 . Best solution would be to use datetime to actually parse the time. This would also deal with impossible dates i.e 29.02 in a non leap year. It would also be nice if in the parsed ds those fields where datetime and not string.