Hi farrio,
There is
no battery in the SX700. When the SX700 is connected to a local network via an (optional) USB WiFi adapter (Yamaha UD-WL01), the date and time are set automatically.
Please go to "MENU > Menu 2 > Time". There you can set the date and time. I hope the "Time" menu item is displayed (unlike "Wireless LAN") even when the SX700 is not connected to a network).
Note that the date/time settings may be lost if the SX700 is unplugged for a few days.
See also the SX700 Reference Manual, page 128. If you don't have the Reference Manual, you can download it here:
>>>
https://uk.yamaha.com/en/products/musical_instruments/keyboards/arranger_workstations/psr-sx700/downloads.htmlBy the way, to my knowledge there are no differences between SX900 and SX700 regarding wireless LAN and date/time settings. However, since I don't own one of these models, I unfortunately don't know whether the "Time" menu item mentioned is
always displayed or only when there is an existing WLAN (WiFi) connection to a local network.
Best regards,
Chris