AMT stands for Amazon Time - Manaus, Campo Grande, Cuiabá, Porto Velho and represents UTC-04:00. Note that AMT is used by 2 different zones, so the correct offset depends on the location you mean.
Ambiguous Abbreviation
"AMT" has 2 different meanings depending on the region.
UTC-04:00
Current time:
--:--:--UTC+04:00
Current time:
--:--:--