What is that?
chronogram 
Epitaph
Ostracon
Abecedarium
A chronogram is a sentence or inscription in which specific letters, interpreted as numerals, stand for a particular date when rearranged.   In the pure chronogram each word contains a numeral; the natural chronogram shows all numerals in the correct numerical order, e.g. AMORE MATVRITAS = MMVI = 2006. 
reach: rather globalalphabetsarchitecturearthistory
Answers by country
chronogram 
Epitaph
Ostracon
Abecedarium
answers
 Germany
Germany135
 Australia
Australia18
 Greece
Greece17
 Poland
Poland4090
 Republic of Ireland
Republic of Ireland25
 the United States
the United States68
 the Netherlands
the Netherlands14
 the United Kingdom
the United Kingdom70
 France
France11
 India
India29
 Italy
Italy11