Change default date value from UNIX epoch to dash

src/components/EmailHeader/EmailHeader.js

@@ -85,7 +85,12 @@ export default function EmailHeader({ datetime, from_name, from_email, to, cc })
 						<Typography variant="body2">{buildEmailNameString(from_name, from_email)}</Typography>
 					</Grid>
 					<Grid item xs={3}>
-						<Typography variant="body2" color="textSecondary" align="right"><RelativeTime value={datetime} /></Typography>
+						<Typography variant="body2" color="textSecondary" align="right">
+							{ datetime === "-"
+								? datetime
+								: <RelativeTime value={datetime} />
+							}
+						</Typography>
 					</Grid>
 				</Grid>
 			</Paper>
@@ -106,19 +111,19 @@ export default function EmailHeader({ datetime, from_name, from_email, to, cc })
 EmailHeader.propTypes = {
 	/** Name of message sender. */
 	"from_name": PropTypes.string,
-	/** Date the message was sent in ISO 8601 format. */
+	/** Any string, number or Date object understood by React Relative Time. See https://github.com/aharshac/react-relative-time#readme. */
 	"datetime": PropTypes.string,
 	/** Email address of message sender. */
 	"from_email": PropTypes.string,
-	/** Array of people the message was sent to */
+	/** Array of objects with name and email keys for message recipients. */
 	"to": PropTypes.array,
-	/** Array of people the message was cc'd to */
+	/** Array of objects with name and email keys for message copies. */
 	"cc": PropTypes.array
 };
 
 EmailHeader.defaultProps = {
 	"from_name": "Name Unavailable",
-	"datetime": new Date(1970, 1, 1, 0, 0, 0, 0),
+	"datetime": "-",
 	"from_email": "Email Unavailable",
 	"to": [],
 	"cc": []