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:
| Episode | Broadcast date | Run time | Viewers (in millions) | Archive |
| --- | --- | --- | --- | --- |
| " Episode 1 " | 23December1967 | 23:45 | 6.8 | 16mm t/r |
| " Episode 2 " | 30December1967 | 23:48 | 7.6 | 16mm t/r |
| " Episode 3 " | 6January1968 | 23:05 | 7.1 | 16mm t/r |
| " Episode 4 " | 13January1968 | 23:46 | 7.8 | 16mm t/r |
| " Episode 5 " | 20January1968 | 24:22 | 6.9 | 16mm t/r |
| " Episode 6 " | 27January1968 | 21:41 | 8.3 | 16mm t/r |
Question:
Which broadcast date has 6.8 million viewers?
Answer:
23December1967