/usr/share/zoneinfo/EST should be the same as
/usr/share/zoneinfo/Canada/Eastern gives the correct time.
timezone-data and/or glibc version needed.
Timezone data is 2006g
glibc is 2.4-r3
please e-mail any such concerns to email@example.com, they maintain said timezone files
Canada/Eastern is *not* the same as EST. EST is standard time year-round, but Canada/Eastern observes daylight saving time. The difference in output is correct (pay attention to the time zone indicator).
Also, it is preferable to choose a city-based zone name (e.g., America/Toronto), which are the canonical names in the tz database, instead of the backward-compatability names (e.g., Canada/Eastern) --- the old names have ambiguity problems that the newer (city-based) names were designed to correct.