I must not understand how subtraction works with DateTime. Using one method, I get 4 days and using another, apparently equivalent, method, I get 5 days duration: 
main::(a.pl:49):    my $first_time_date_time=DateTime::Format::ISO8601
+->parse_datetime($first_time);
                                                                      
+                                                                     
+                    DB<2> p $first_time
2013-08-01T20:10:31
                                                                      
+                                                                     
+                    DB<3> n
main::(a.pl:50):    my $last_time_date_time=DateTime::Format::ISO8601-
+>parse_datetime($last_time);
                                                                      
+                                                                     
+                    DB<3> p $last_time
2013-08-06T20:09:34
                                                                      
+                                                                     
+                    DB<4> n
main::(a.pl:51):    my $duration=$last_time_date_time->subtract_dateti
+me($first_time_date_time);
                                                                      
+                                                                     
+                    DB<4> 
main::(a.pl:52):    my $days=$duration->days;
                                                                      
+                                                                     
+                    DB<4> p $duration
DateTime::Duration=HASH(0x1a2f268)
                                                                      
+                                                                     
+                    DB<5> p $duration->in_units('days')
4
                                                                      
+                                                                     
+                    DB<6> x $duration->deltas()
0  'months'
1  0
2  'days'
3  4
4  'minutes'
5  1439
6  'seconds'
7  3
8  'nanoseconds'
9  0
                                                                      
+                                                                     
+                    DB<7> $d=$last_time_date_time->delta_days($first_
+time_date_time)

                                                                      
+                                                                     
+                    DB<8> p $d
DateTime::Duration=HASH(0x1e1e2e8)
                                                                      
+                                                                     
+                    DB<9> p $d->in_units('days')
5

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In reply to Inconsistent results of subtraction with DateTime? by jabowery

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