How do I update the dates (by 30 days) in the files going to that specific location in unix? Can awk or sed help ?

File format is as below -

Thomson: xyz  

Format: 1  

Character\_set: ASCII8  

File\_type: event\_file  

File\_subtype: mobile\_call  

File\_group\_number: 1  

File\_in\_group\_number: 1  

Total\_files\_in\_group: 19  

Source\_ID: source  

Tag: tag -v13 

This file produced by GTFplaintext 0.1:

```
Event: "61765","1","2014/01/03-13-00-00.00",,"GBP",,,,,,,,,,"61765","0345351816","1407",,,,,,,,,,,,,,,,,,,,,
Footer: text_data_transfer_file
AuditValue_1: 1
AuditValue_2: 0
End: text_data_transfer_file
Lines: 15
Characters: 351
Checksum:
Security_checksum:
End_of_file:

```

In the above file I need to go to the line starting with 'Event:' and update the date  

 "2014/01/03-13-00-00.00" by 30 days (only date needs to be updated, while time can remain same).  

There are 20k such files in a directory, for which the dates have to be updated.