Yes. As long as you set the schedule while your phone/tablet has Wi-Fi or cellular data access, the schedule will be transferred to the cloud.
Therefore, even if your phone is OFF, has no cell service/reception, or is in Airplane Mode, the set schedules will still activate. Schedules activate in the timezone the devices were configured within, regardless of your phone's location.
However, you will not be able to use the CE Smart App to manually turn on/off your Smart Devices if your phone does not have service or is in airplane mode. Additionally, when your phone/tablet does not have an internet connection available, you will not receive any set "execution notifications" for timers. Notifications and remote device control will resume when your phone/tablet is connected to the internet again.
Smart Devices must remain connected to the internet for set schedules to execute properly and for remote control of devices.
Note: Execution Notification is available in CE Smart V 2.6.5 and later; this can be turned on within schedule/timer settings. When turned on, you will receive a notification each time the schedule activates.