QGIS: How to convert date values with format d-m-yyyy in a string field, into date values with format yyyy-mm-dd in a date field?

Question

I have date values with the format d-m-yyyy in QGIS. They are in string field. I want to convert them into date values with the format yyyy-mm-dd. I want them in a date field.

Can this be done without doing something in Python?

Answer 1

I would recommend to use the Field calculator.

Expression would be:

to_date(
  concat(regexp_substr("old_date", '([^-]+$)'), 
         '-', 
         lpad(regexp_substr("old_date", '[-](\\d*)[-]'), 2, 0), 
         '-', 
         lpad(regexp_replace("old_date", '([-].*$)', ''), 2, 0)
   )
 )

Please replace "old_date" by your actual string field.