A little about SD CARD and RTC - e2002/yoradio GitHub Wiki

Starting from v0.9.300, playback in SD CARD mode can work without an Internet connection:

• When loading in SDCARD mode, the player can operate without a network connection, and the network connection happens in the background.
• In the absence of a connection, if the RTC module is configured correctly, the time is displayed correctly. More details in examples/myoptions.h#L86
• The RTC module has three parameters - RTC_SDA, RTC_SCL, RTC_MODULE. All three must be specified.
• To use SDCARD without an internet connection, the presence of an RTC is not mandatory. If the RTC module is not configured or is absent, the time starts from 00:00 and synchronizes upon resuming the internet connection.
• When the connection is lost in WEBRADIO mode, the PLAY button and the MODE button restart the ESP in SDCARD mode.
• When booting in AP mode, the PLAY button and the MODE button restart the ESP in SDCARD mode.
• The * button on the IR remote switches the ESP to SDCARD mode and back.