With the transition to the registered-based census method the new reference date is 1 January instead of 31 March.

Reasons for a new reference date are:

-  previous date was chosen due to practical reasons (favourable weather

    conditions for fieldwork)

-  administrative sources are as a rule linked to the calendar year

-  easier comparability with annual demographic surveys

-  greater regulation of administrative sources at the end of the calendar year

-  experience of countries already conducting registered-based censuses.