The Period/Date options are driven by the GL Reconciliation Rule that is linked to the GL Reconciliation.
In the example below, the options are greyed out because they are not included in the ‘Range’ on the GL Reconciliation rule:

In the GL Reconciliation rule example below, the range does not require a specified period or date, therefore these options are greyed out on the GL Reconciliation:

The rule would need to be set with the below value selected to allow the freedom of selecting the dates when creating a GL reconciliation.
