Here you go
dt = "10.18.12 klo 04.00.00 ap."
strptime(gsub(' ip.',' PM',gsub(' ap.',' AM',gsub(' klo ',':',dt))),format='%m.%d.%y:%I.%M.%S %p')
[1] "2012-10-18 04:00:00"
dt = "10.18.12 klo 04.00.00 ip."
strptime(gsub(' ip.',' PM',gsub(' ap.',' AM',gsub(' klo ',':',dt))),format='%m.%d.%y:%I.%M.%S %p')
[1] "2012-10-18 16:00:00"