Letter of Credit Forum

if the drats say 120 days from the invoice date in a l/c , and last date of shipment is 30 th june what will the field available by: say- by acceptance or by negotiation? also whatwill be the expiry date of the l/c . willit be after 120 days or can it be earlier say 30 days from last date of shipment? please clarify as i am confused..