Hello Azmimusa,
To help us better assist you, can you let us know if the calendar displays correctly in the Calendar app, but not on the Lock Screen? Is Islamic calendar selected under Settings > Calendar > Alternate Calendars, on your device?
The above information will help us determine how to proceed: Customize your calendar on iPhone
Go to Settings
> Calendar, then choose the settings and features you want.
If the calendar is correctly selected, but doesn't display correctly on the Lock Screen, please check out this link which outlines options to personalize your iPhone Lock Screen, and may help: Personalize your iPhone Lock Screen
You can personalize your Lock Screen by choosing a wallpaper, customizing the colors and fonts, layering subjects of photos in front of the time, and much more. You can also add widgets with information from your favorite apps to your Lock Screen, such as today’s headlines, the weather, and calendar events.
Thanks!