Validate the datetime value

Validate the value should be well-formated value e.g. year-month-day 2026-05-06

MySQL approach

Verify the value of DAY() is NULL

SELECT `my_date_column`
FROM `my_table`
WHERE DAY(`my_date_column`) IS NULL;

SELECT `my_date_column`, STR_TO_DATE(`my_date_column`, '%Y-%m-%d')
FROM `my_table`
WHERE
STR_TO_DATE(`my_date_column`, '%Y-%m-%d') IS NULL;

Verify the value should be year/month/day format

SELECT `my_date_column`, STR_TO_DATE(`my_date_column`, '%Y/%m/%d')
FROM `my_table`
WHERE
STR_TO_DATE(`my_date_column`, '%Y/%m/%d') IS NULL;

Verify the value should be hour:minute:second format e.g. 16:03:06

SELECT `my_time_column`, STR_TO_DATE(`my_time_column`, '%H:%i:%S') 
FROM `my_table`
WHERE
STR_TO_DATE(`my_time_column`, '%H:%i:%S') IS NULL;

Verify the value should be year-month-day hour:minute:second format e.g. 2026-05-06 16:03:06

SELECT `my_time_column`, STR_TO_DATE(`my_time_column`, '%Y-%m-%d %H:%i:%S') 
FROM `my_table`
WHERE
STR_TO_DATE(`my_time_column`, '%Y-%m-%d %H:%i:%S') IS NULL;

Verify the value not start with four number, which means year. Not recommended!

SELECT `my_date_column`
FROM `my_table`
WHERE `my_date_column` NOT REGEXP '^[0-9]{4}';

PHP appracoh

Using PHP strtotime function

Excel approach

1. Validate the total length of cell value is equal to 10 e.g. =IF(LEN(B2)<>10, TRUE, FALSE)
2. Validate the positions of the - symbols
3. Combined the above condition, the verify formula is: (If the cell value is well-formatted, the formula returns true)

=NOT(
     IF(OR(
           ISERROR(FIND("-", B2, 1)), 
           ISERROR(FIND("-", B2, 6)), 
           IF(LEN(B2)<>10, TRUE, FALSE)
           ), TRUE, FALSE)
 )