public String getDefaultTimeZone() {
        return this.defaultTimeZone.toZoneId().toString();
    }
Some dates in some file formats do not have a timezone.
Tika correctly stores these without a timezone, e.g. 'yyyy-MM-dd'T'HH:mm:ss'
This can be a problem if end points expect a 'Z' timezone.
This filter makes the assumption that dates without timezones are UTC
and always modifies the date to: "yyyy-MM-dd'T'HH:mm:ss'Z'"

Users can specify an alternate defaultTimeZone with
{@link DateNormalizingMetadataFilter#setDefaultTimeZone(String)} to apply
if the file format does not specify a timezone.
tika-core/src/main/java/org/apache/tika/metadata/filter/DateNormalizingMetadataFilter.java