+=head1 HISTORY
+
+Since OpenSSL 1.1.1, the program follows RFC5280. Specifically,
+certificate validity period (specified by any of B<-startdate>,
+B<-enddate> and B<-days>) will be encoded as UTCTime if the dates are
+earlier than year 2049 (included), and as GeneralizedTime if the dates
+are in year 2050 or later.
+