You can make DIY Dot Matrix Clock (ESP Matrix) no needed an internet connection only use the RTC module to retrieve date time value. Using this app for directly uploading firmware to ESP8266 and configure with simple interface.

ESP Matrix device features:
- Display Clock with a beautiful animation icon
- Display Reminder-1
- Display multiple Reminder-2 to Reminder-5 (Pro Version)
- Display Calendar (Pro Version)
- Display Hijri Calendar (Pro Version)
- Display Muslim Prayer times
- Display Temperature
- Able to configure Brightness display
- Able to change font size (Pro Version)
- Able to configure scroll text speed

App features:
- Upload firmware directly from your Android phone to ESP Matrix Offline
- Set WiFi connectivity of ESP Matrix devices through the app
- Configure ESP Matrix device through an simple interface

Tutorial to make hardware ESP Matrix:
https://www.instructables.com/id/IoT-Smart-Clock-Dot-Matrix-Use-Wemos-ESP8266-ESP-M/

Note:
* Required permission to access devices Location for WiFi discovery (not for GPS location)