public static Instant parseStandardDate(final MessageHeaders headers, final String headerName) {
        if (headers == null) {
            return null;
        }
        final Header header = headers.getFirstHeader(headerName);
        if (header == null) {
            return null;
        }
        return parseStandardDate(header.getValue());
    }
Parses an instant value from a header with the given name.

@param headers message headers
@param headerName header name

@return the parsed instant or null if input could not be parsed

@since 5.2
httpclient5/src/main/java/org/apache/hc/client5/http/utils/DateUtils.java