Not sure why the time difference is an issue. But it is my understanding wifi is available almost everywhere in Vietnam.

Experts will have more advice / info -- I haven't actually visited VN myself but have several friends/relatives who have multiple times (and two friends who live there) and all just used the mostly free wifi everywhere.

Wifi is freely available in hotels everywhere. In the cities at least, it is pretty fast 25-50mbps. I have visited Vietnam many times and have never see portable wifi offered anywhere. Not sure how much use it would be anyway. Unless of course you plan on using Skype in the back of a taxi or walking along the street.

Assuming you have an unlocked phone, the easiest and cheapest way to online access is to buy a SIM card on arrival. They are pretty cheap.

For GPS just download google offline maps for Vietnam when on wifi and it will work fine whether or not you are connected.

The Viet spend their time playing with their smartphone (even while driving a scooter), so Wifi is available practically everywhere including bars and restaurants, even in homestays. You just have to buy a SIM card (sold in airports or in the streets, the latter with signs "SIM cards"

Not a big deal but I'm still curious -- why would the time of day (or night, or wee small hours) make a difference?

I guess we are just having a failure to communicate. I did read your response . . . but since wifi is available most everywhere AND is a 24/7 thing-y, the time zone you are in and the time zone your contacts are in wouldn't make any difference.

janisj, while I appreciate your comments I don’t get your obsession with my post. This isn’t the first time you’ve essentially questioned in depth or made weird posts to me. Suffice it to say, it’s of no importance to you, understand or not.
thanks to others who have responded and not felt the need to grill me on my phone call needs.

Just thought this post should be pointed out, as it mangles the difference between WiFi and a SIM card. You don't need anything other than your regular smartphone to use WiFi at a bar, restaurant, hotel, etc. To use cellular data service when you're NOT at such a place, e.g., riding in a taxi or walking around on the street, you need to have an unlocked phone and buy a SIM card. Crellston's very helpful post below gets it right: