Problem with the form after enabling the https SSL certificate

After switching on the ssl certificate page, https appeared in the value data-start_date = 15-02-2018 field. Until now, the user had the opportunity to choose the date of arrival and departure from the calendar. In the administration panel, I have in the value field
General --> Value
data-start_date=<?php echo date("d-m-Y"); ?>
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How to solve this problem?

Hi sylwekb,
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Do you have v5 or v6 ?
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if its v6 then v6 does not take parameters in this format, you will need to use the calendar field advanced settings or this:

data-start_date:{date:d-m-Y}

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Best regards

I've marked the above version 6
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I have in the value field
General --> Value

data-start_date=<?php echo date("d-m-Y"); ?>
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Is this correct?

No, this is not correct!
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What are you trying to do ? set the date field start date ? if yes then the calendar field has a "Start date" setting under the "Advanced" area, just add {date:Y-m-d} there.
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Best regards