Date must be in the format YYYY-MM-DD or YYYY-MM-DDTHH:MM:SS(((+|-)HH:MM)|Z).
This error occurs when you provide dates that are not in the standard ISO-compliant format.
As an example, February 29, 2008, 1:10:30 p.m. in London should be expressed as:
The ISO standard is based on Greenwich Mean Time (GMT). If you're in Mainland Europe, you are 1 hour ahead of GMT. This would be indicated by "+1:00" in the formula above.
One common reason why this error occurs is:
If you are using Microsoft Excel to manage your data, you can format your date columns as text to prevent Excel from automatically reformatting them. To do this: