scoreboard objectives add time dummy
scoreboard players set @e[,score_commandBlock_min=1,score_time_min=0,score_time=0] time 60
execute @e[score_commandBlock_min=1,score_time_min=1,score_time=60] ~ ~ ~ scoreboard players remove @e[score_command_Block_min=1] time 1
execute @e[score_time=0] ~ ~ ~ summon PrimedTnt ~ ~ ~
kill @e[score_time_=0,score_commandBlock_min=1]