DHCP assigns a new IP address when the Time Zone changes

I have a device linux-based. Through a webpage I can change the time zone runtime. This device takes the IP and NTP address from a DHCP.

Using two different servers I have two different behaviours:

  • dnsmasq With the below configuration every time the change the time zone, after the reboot of the device, his IP address remain the same.

    dnsmasq --bind-interfaces --interface=eth0 \
            --dhcp-range=192.168.0.100,192.168.0.250,48h \
            --dhcp-option=42,192.168.0.4
    
  • dhcp3-server (On Debian): With the below configuration /etc/dhcp.conf every time the change the time zone, after the reboot of the device, his IP address is different.

    option domain-name "domain.test.com";
    option domain-name-servers 192.168.104.1;
    option ntp-servers 192.168.104.1;
    
    default-lease-time 86400; #24h
    max-lease-time 172800; #48h
    
    ddns-update-style none;
    
    subnet 192.168.104.0 netmask 255.255.255.0 {
       range 192.168.104.50 192.168.104.150;
        option routers 192.168.104.1;
    }
    

The lease time is different but the time zones change have been done with jumps of 12h max.

My question is: Why the IP of device change? Thank you in advance for the explanation and/or indications.