Convert string to date and get Day

Question

How to convert string Date to Date?

I have a string "20210712" in the format yyyymmdd how to convert it into date...And how to get the day of It.

Answer 1

You can do it with use of DateTimeFormatter and LocalDate:

DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMdd");
LocalDate date = LocalDate.parse("20210712", formatter);
System.out.println(date);
System.out.println(date.getDayOfWeek());
System.out.println(date.getDayOfMonth());
System.out.println(date.getDayOfYear());

Output:

2021-07-12
MONDAY
12
193

Answer 2

You can use String.substr to split the date string into its components. We'll use the + shorthand to convert each component into a number, then create a new Date object from it, using the Date constructor new Date(year, monthIndex, day).

NB: In JavaScript we pass the monthIndex to the Date rather than the month number, so July is represented as monthIndex = 6;

To get the day of the month from your date, you'll need Date.getDate().

To get the day of the week from your date, you'll need Date.getDay(), this will return 0 - 6 (Sunday (0) -> Saturday (6))

To get the day of the week as a string from your date, you can use Intl.DateTimeFormat, this will return 'Monday' -> 'Sunday'.

const timestamp = "20210712";
const year = +timestamp.substr(0,4);
const monthIndex = +timestamp.substr(4,2) - 1;
const day = +timestamp.substr(6,2);

console.log("Timestamp:", timestamp)
console.log("Date components:", JSON.stringify({ year, monthIndex, day }))

const date = new Date(year ,monthIndex, day);
console.log('Date:', date.toDateString());
console.log('Day of Month:', date.getDate());

// Sunday - Saturday : 0 - 6
console.log('Day of Week (0-6):', date.getDay());
console.log('Day of Week (string):', new Intl.DateTimeFormat('en-US', { weekday: 'long'}).format(date))