GTD lets you express a horizon. It suits a level you expect to matter this week but not next month, and it avoids the main hazard of good-till-cancelled orders, which is a forgotten order firing months later into a different market.
Brokers differ in whether a GTD order works in extended-hours and how corporate actions adjust it, so check the fine print before relying on one across a dividend or split.
Example: you set a GTD buy at 90.00 expiring Friday. On Wednesday the stock trades 90.00 and you fill. Had you used a day-order, you would have re-entered it manually three times, with a real chance of forgetting on the day it mattered.
Related: good-til-time, order-expiry