By using finalize and dispose methods and calling the proper free method.
8,806 (64 direct, 8,742 indirect) bytes in 2 blocks are definitely lost in loss record 18,051 of 18,131
at 0x4C2DB9D: malloc (vg_replace_malloc.c:299)
by 0x9A0C90E: g_malloc (gmem.c:94)
by 0x9A26A55: g_slice_alloc (gslice.c:1025)
by 0x9A26A95: g_slice_alloc0 (gslice.c:1051)
by 0x99E8DC4: g_date_time_alloc (gdatetime.c:428)
by 0x99E95C1: g_date_time_new (gdatetime.c:957)
by 0x99E97B2: g_date_time_new_local (gdatetime.c:1012)
by 0x4251F4: multi_choice_changed (gcal-date-chooser.c:419)
by 0x9567F16: g_cclosure_marshal_VOID__PARAM (gmarshal.c:1832)
by 0x95638B9: g_closure_invoke (gclosure.c:804)
by 0x957FD25: signal_emit_unlocked_R (gsignal.c:3635)
by 0x957F05C: g_signal_emit_valist (gsignal.c:3391)
https://bugzilla.gnome.org/show_bug.cgi?id=772272