How to sail rafts in Breath of the Wild

There's no in game option to change it.

American version

• Temperature is Fahrenheit
• AM/PM Clock 12:00 - 11:59 am/pm

European version

• Temperature is Celsius
• 24 Hour Clock 0:00 to 23:59

some stupid workaround:

Use an account tied to a different region, or change the consoles region.

EDIT :

It seems you have a hardcopy version of the game which mean there is nothing you can do except buying EU version of the game.

Easier Way :

(°F - 32) x 5/9 = °C

If you're fast, you can run up to frogs near some ponds and catch them on the go. That's also possible with lizards, but a lot more difficult.

But you're right, you can't simply waltz up to most critters as you'll scare them off. You need to sneak up to them slowly. Crouching helps, as does moving slowly. Remember that you have a sound meter that shows you how much noise you're making. Make sure to keep an eye on it and keep the line as flat as possible and you should be able to sneak up to bugs and catch them. You can easily catch 3-4 fireflies at night simply be crouching around them.

The noise meter is the purple line in the bottom right corner. The more erratic it is, the more noise you're making. Handy for sneaking up on enemies too.