Hand out the time zone from your ISC DHCP Server

Add the following lines to the top of your dhcpd.conf file

option PCode code 100 = text;
option TCode code 101 = text;
option PCode "EST5EDT4,M3.2.0/02:00,M11.1.0/02:00";
option TCode "America/NewYork";

In this case, the string is interpreted as a timezone that is normally five hours behind UTC, and four hours behind UTC during DST, which runs from the second Sunday in March at 02:00 local time through the first Sunday in November at 02:00 local time. Normally the timezone is abbreviated “EST” but during DST it is abbreviated “EDT”.

Additional examples:

option PCode code 100 = text;
option TCode code 101 = text;
option PCode "CST6CDT5,M3.2.0/02:00,M11.1.0/02:00";
option TCode "America/Chicago";

option PCode code 100 = text;
option TCode code 101 = text;
option PCode "NZST-12NZDT,M9.5.0/2,M4.1.0/3";
option TCode "Pacific/Auckland";

Reference:  https://tools.ietf.org/html/rfc4833