Saturday, October 31.
Friday the 30th is the party.

The dates around it

Two notes for a Saturday. The trick-or-treating night is Friday the 30th — a calendar that says "Halloween party, Oct 31" will send people to the wrong evening if the party starts before sunset. And November 1 and 2 are not a Halloween extension: they are All Saints' Day and All Souls' Day, and in Mexico and among Mexican communities they are the start of Día de los Muertos, which is a different observance with its own dates and its own reasons.

Día de los Muertos, in case that is the one you meant

If you are looking for the Mexican dates rather than the American one: November 1 and 2, 2026. It is commonly called Day of the Dead in English, and it is the celebration the ofrenda is built for. If your question was in Spanish, that is the page you want.

Trick-or-treating hours

There is no national rule, and that is not an oversight: the hours are set by local ordinance and differ from one town to the next. What is universal is the window — dusk on Friday the 30th until the early hours of Saturday the 31st. Check your own municipality rather than a national list, and do not plan a party for a window you have not confirmed.

The files behind the party

Halloween generates a burst of images, and they have to go somewhere specific:

• Invitations and flyers get sent by email, and an email attachment has a ceiling. Gmail counts 25 MB for all attachments together — and because the encoding adds about a third, a 25 MB attachment is roughly an 18 MB file. Our Gmail attachment limit guide has the numbers for the other providers too.
• Costume photos come off a phone at 3–6 MB each. A group photo set for a group chat, or a gallery on a party page, is usually where the size problem shows up. The image compressor handles a whole batch and gives back a ZIP.
• Print needs a different number: pixels per inch, not bytes. A flyer printed at A4 wants roughly 150 DPI, and a photo printed at 300 pixels per inch looks like a mosaic no matter how large the file is.

All of it runs locally: the photos and the flyers never leave the device, which is worth something when they are photographs of children.

A short checklist

1. Put the date on the invite in full — "Saturday, October 31" — because a bare "Oct 31" is how half the party ends up on the wrong night.
2. Say when the trick-or-treating window is, not just that Halloween is on the 31st.
3. Compress the images once, at the size the channel needs, and reuse the small file everywhere.
4. Print at 150 DPI for a flyer and 300 DPI for a photo.
5. Keep the original — the compressed copy is for sending, the original is for the album.

What this guide is not

• Not a list of costume ideas. The recipes and the memes are somebody else's business — ours is the file handling.
• Not a local calendar. Trick-or-treating hours and any local restrictions come from your municipality.
• Not a party planner. We do the bytes; the guest list is yours.