Hi Yosi,
By 3CX Cloud I am going to assume you mean a 3CX system hosted in the cloud although please specify.
In 3CX go to >> Settings >> Timezone, Office hours & Holidays >> Global Time Zone.
Also double check your NTP server settings,by default they are on pool.ntp.org:
Management Console >> Settings >> Parameters >> search for TIME_NTP_SERVER . On the value you will see the domain pool.ntp.org.