Nokia 5230 - Manual (Page 148)

Q: Why do I get the error message Expired certificate or Certificate
not valid yet when I am installing a downloaded application?
A: If Expired certificate or Certificate not valid yet is displayed, even if the
certificate should be valid, check that the current date and time in your device are
correct. You may have skipped the setting of date and time when starting the device
for the first time, or the mobile network may have failed to update these settings
to your device. To resolve this, select Menu > Settings and Phone > Phone
mgmt. > Factory settings. Restore the factory settings, and when the device
restarts, set the correct date and time.
23. Green tips
Here are tips on how you can contribute to protecting the environment.
Save energy
When you have fully charged the battery and disconnected the charger from the
device, unplug the charger from the wall outlet.
You do not need to charge your battery so often if you do the following:
● Close and disable applications, services, and connections when not in use.
● Decrease the brightness of the screen.
● Set the device to enter the power saver mode after the minimum period of
inactivity, if available in your device.
● Disable unnecessary sounds, such as keypad and ringing tones.
Green tips
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