I will give you some examples:
SELAMA
Dia pergi selama satu minggu. (he was gone for a week)
Saya tinggal di Jawa selama tujuh tahun. (I lived in Java for seven years)
Dia telah mengantri selama tiga jam. (she had been waiting in line for three hours)
SAAT/ KETIKA
Saya terkejut saat sedang bermain dan tiba-tiba ibu berteriak. (I was shocked when I was playing and then suddenly my mother screaming)
Ketika saya berusia sepuluh tahun, saya sangat takut ular. (when I was ten, I was so afraid of snakes)
Kira-kira dua hari yang lalu, pada pukul tujuh, seseorang mengirim setangkai bunga mawar ke kantorku. Saat itu, aku sangat terkejut ketika menerimanya. (about two days ago, at seven, someone sent a rose to my office. At that time, I was very surprised when received it)
saat itu= at that time
ketika= when
saat= when/while
KALAU
kalau aku jadi kamu, aku tidak akan pergi kesana. (If I were you, I wouldn't go there)
kalau sudah besar, kamu mau jadi apa? (when you grow up, what do you want to be?)