Real time clock on Pico (rev 1.4)

Hi

I'm building a Programmable Timer Switch (Synchronizing time with DCF77 - from time to time) on espruino Pico so I need a quite accurate clock.
Do I need a external RTC (like DS1307 or DS3231) or internal crystal is accurate enough for a clock?
I'm quite confused because here we've got: https://www.espruino.com/Pico+Clock

While the Pico has an RTC built in, by default it doesn't have an accurate watch crystal and so uses its internal oscillator which isn't that accurate. It won't keep proper time over a month

but, on the other hand, there is a clock frequency crystal in schematic - which should generate very accurate time

Thanks for your help