How to sync times of two devices with Android NTP?

We have 2 android devices running same application that users see their GUI. Time synchronization is curicial for us. To make them have same time we have the settings as below. Use these commands in boot and after every 5 minutes but it seems after 8 9 hours of uptime two android devices have different times with respect to their seconds. ex: busybox watch -n 1 date DEVICE 1: (Android 6 Marshmallow) 2020-03-10 09:16:33 DEVICE 2: (Android 6 Marshmallow) 2020-03-10 09:16:38 settings put global ntp_server pool.ntp.org settings put global auto_time 0 settings put global auto_time 1 After that we also tried below commands but not worked settings put global ntp_polling_interval 10 settings put global ntp_pollinginterval 10 settings put global ntppollinginterval 10 Any suggestions?