First of all, I would like to point out to them that we also have an English community. Other users may have the same question and therefore it would be good to post in the English community. Next time, just change the language of the page.
The validity of the subscriptions is always 1 month from the date of purchase. For example, with or without the leap year in February, it is like this: purchase on February 28 - valid until March 27 (Same date, just one month later - 1 day).
For further questions you can also contact our Contact Center on 0848 44 66 88 (CHF 0.08/min.).
Thank you for your understanding and have a happy new year.