WooCommerce lets you set a coupon "Expiry date" but not an exact time. This lightweight plugin adds a "Coupon expiry time" field (HH:MM, 24h) to the coupon edit screen.
When both date and time are set, the coupon will expire on that date at the time you specify.

Key points

• Works alongside WooCommerce’s native coupon expiry date.
• Time is stored internally as seconds since midnight and combined with the date.
• No changes to your theme or checkout templates required.