Raspberry PICO Mode D'emploi page 75

/* Simple demonstration of setting and printing the current time */
/* The initial time will need to come from an RTC, NTP, or user */
/* Released to the public domain by Earle F. Philhower, III
<earlephilhower@yahoo.com> */
#include <time.h>
#include <sys/time.h>
void setup() {
Serial.begin(115200);
delay(5000);
struct timeval
tv.tv_sec = 1611198855;
tv.tv_usec = 0;
settimeofday(&tv, nullptr);
}
void loop() {
time_t now;
char buff[80];
time(&now);
strftime(buff, sizeof(buff), "%c", localtime(&now));
Serial.println(buff);
delay(1000);
}
tv;
// Jan 21, 2021 3:14:15AM ...RPi Pico Release;