即日

1. Origins, structure, and basic meaning

• Structure: 即日, read そくじつ, means the very day on which something takes place.
• Basic usage: It describes same-day actions, such as shipping on the day of an order or announcing results on the day of an interview.

2. Common pitfalls and similar expressions

• Same-day does not mean instantaneous
  • 即日発送 means shipping on the day an order or similar request is received; it does not guarantee shipping at that very moment.
  • 即座に means immediately, on the spot.