如何在不以不同格式结束的情况下将 UTC DateTime 转换为本地 DateTime

Question

I have specific DateTime values in this format ' YYYY-MM-DDThh:mm:ss.ms ' (eg ' 2022-05-10T13:44:00.0000000 ') and I need to convert them to local DateTime (which is UTC+2 for me) without changing the format (so ' 2022-05-10T15:44:00.0000000 ' is the desired result (even better would be without the milliseconds but that would just be the icing on the cake)).

I've searched far and wide but every alleged solution I find either changes the format or doesn't change the time at all.

This is what I have right now, it successfully converts the time to local time but by running it through.toISOString() to get the original format back it converts it back to UTC time.

//Input: event.start.dateTime = '2022-05-10T13:44:00.0000000'

let startDateTime = new Date(event.start.dateTime);
startDateTime.setMinutes(startDateTime.getMinutes() - 
startDateTime.getTimezoneOffset());
document.getElementById('ev-start').value = 
startDateTime.toISOString().slice(0,16);

//Output: '2022-05-10T13:44:00.000Z'

Answer 1

I couldn't find a clean and satisfying solution so I decided to just to the formatting myself. Here's what I ended up with:

Input: ' 2022-05-10T13:44:00.0000000 '

let startDateTime = new Date(event.start.dateTime);
startDateTime.setMinutes(startDateTime.getMinutes() - 
startDateTime.getTimezoneOffset());
let localStartDateTime = startDateTime.getFullYear() + "-" + 
       (startDateTime.getMonth() + 1).toString().padStart(2, '0') +
       "-" + startDateTime.getDate().toString().padStart(2, '0') + 
       "T" + startDateTime.getHours().toString().padStart(2, '0') + 
       ":" + startDateTime.getMinutes().toString().padStart(2, '0') 
       + ":" +
       startDateTime.getSeconds().toString().padStart(2, '0');
       document.getElementById('ev-start').value = 
       localStartDateTime;

Output: ' 2022-05-10T15:44:00 '

Answer 2

Hope this helps

 const startDateTime = new Date('2022-05-10T13:44:00.0000000'); const outputDateTime = new Date(startDateTime.toString()).toISOString().slice(0, 19); //document.getElementById('ev-start').value = outputDateTime console.log(outputDateTime);