so to make the call last 1 minute and end with cause
SWITCH_CAUSE_ALLOTTED_TIMEOUT
(which happens to be the default so you can omit it unless you need another cause.)
<action application="sched_hangup" data="+60 alloted_timeout"/>
Also if you omit the '+' character the value will be considered the
absolute epoch time you wish the call to end.
Once a call is already up you can do it from the sched_hangup api command
from xmlrpc or the command cli.
do a show channels to get the uuid of the call then enter
sched_hangup +60 <uuid> alotted_timeout
all the params
besides uuid have the same meaning as the dialplan app.