Older or stripped-down systems may support only the TZ values required by POSIX, which specify at most one start and end rule explicitly in the value. For example, TZ='EST5EDT,M3.2.0/02:00,M11.1.0/02:00' specifies time for the eastern United States starting in 2007. Such a TZ value must be changed whenever DST rules change, and the new value applies to all years, mishandling some older timestamps. COUNT 5
QSN1 Less sophisticated systems might just support a TZ value with one start rule and how many end rules? ANS1 one QSN2 When must TZ values be changed on an older system? ANS2 whenever DST rules change QSN3 What does the TZ value EST5EDT,M3.2.0/02:00,M11.1.0/02:00 specify? ANS3 time for the eastern United States starting in 2007 QSN4 What years will a new TZ value apply to? ANS4 all years QSN5 What's might a new TZ value mishandle when it changes with new DST rules? ANS5 older timestamps