Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Locomotive | Delivered as | Entered service | Owner | Status |
| --- | --- | --- | --- | --- |
| H1 | T413 | 20 December 1968 | Pacific National - Rural and Bulk | In Service |
| H2 | T414 | 7 January 1969 | Pacific National - Rural and Bulk | In Service |
| H3 | T415 | 7 February 1969 | Pacific National - Rural and Bulk | In Service |
| H4 | T416 | 24 February 1969 | Pacific National - Rural and Bulk | In Service |
| H5 | T417 | 14 March 1969 | Pacific National - Rural and Bulk | In Service |
Question:
What is the Entered service date of the H1 Locomotive?
Answer:
20 December 1968