meta_query not working on live site

Question

I have the following query_args to fetch events: -> either it's a single event (only start date), so it checks if the start date is between the start of the month AND the end of the month -> or it's a duration event (start + end date), so it checks if the start date is smaller than the start of the month AND the end date is bigger than the start of the month (-> outputs if a event is currently ongoing)

$args = array(
    'numberposts'   => -1,
    'post_type'     => 'event',
    'orderby' => 'meta_value',
    'meta_query' => array(
        'relation' => 'OR',
        // single event
        array(
            'relation' => 'AND',
            array(
                'key' => 'date_start',
                'value' => $firstDayThisMonth,
                'compare' => '>='
            ),
            array(
                'key' => 'date_start',
                'value' => $lastDayThisMonth,
                'compare' => '<='
            )
        ),
        // duration event
        array(
            'relation' => 'AND',
            array(
                'key' => 'date_start',
                'value' => $firstDayThisMonth,
                'compare' => '<='
            ),
            array(
                'key' => 'date_end',
                'value' => $firstDayThisMonth,
                'compare' => '>='
            )
        )
    ),
    'order' => 'ASC'
);

This worked flawlessly on my dev-Server, but on production it doesnt output any events anymore. I have to remove the //duration event array to output the single events, but both queries wont work together. Any ideas?

Answer 1

My reputation is too low for me to comment so I'll do it this way.

Make sure that the date format inside 'value' is the same as the date formats inside the database fields. Also don't forget to add the 'type' => 'DATE' to your query. An example of some code that I've used in the past:

$queryArgs['meta_query'] = [
    [
        'relation' => 'OR',
        [
            'key' => '_ys_brochures-offline-date',
            'value' => date('Y-m-d'),
            'compare' => '>',
            'type' => 'DATE' // notice the 'DATE'
        ],
        [
            'key' => '_ys_brochures-offline-date',
            'compare' => 'NOT EXISTS',
        ],
    ]
];