This example demonstrates the use of LwIP SNTP module to obtain time from Internet servers. See the README.md file in the upper level 'examples' directory for more information about examples.

Obtaining time using LwIP SNTP module

ESP8266 connects to WiFi and obtains time using SNTP. See initialize_sntp function for details.

Working with time

To get current time, gettimeofday function may be used. Additionally the following standard C library functions can be used to obtain time and manipulate it:

gettimeofday
time
asctime
clock
ctime
difftime
gmtime
localtime
mktime
strftime

To set time, settimeofday POSIX function can be used. It is used internally in LwIP SNTP library to set current time when response from NTP server is received.

Timezones

To set local timezone, use setenv and tzset POSIX functions. First, call setenv to set TZ environment variable to the correct value depending on device location. Format of the time string is described in libc documentation. Next, call tzset to update C library runtime data for the new time zone. Once these steps are done, localtime function will return correct local time, taking time zone offset and daylight saving time into account.