I will upload some binaries which you can upload without the compiling.
Formerly i use this firmware and its options for my SmartHome integration with ioBroker from where I script everything i want to control or measure. And it isn’t completely ready, so if you want to contribute something …
Here you can see the Webinterface and where you had to set up your Display
Even the time display is a simple crontab in ioBroker (probably you will use the standard crontab to achieve this) which sends the actual time to the mqtt broker to the corresponding topic which the display listens for new text.
You can find the whole source on GitHub or you can use the binaries i provide which you can upload by esptool.py or the graphical pendant esptool-gui which you can find here on hackaday.io.
The App i used in the Video is MQTT Dash which you can find on Android Playstore
Each widget in MQTT Dash is connected to one MQTT topic of the display. It publishes the messages with a QoS of 1 and as retained message so if the display reboots or something else happend then it restores its state from the retained messages it receives on subscribing to the display topics.
Read more: ESP8266 MAX7219 Dot Matrix Display