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:
| Event | PDT (-7 UTC) | MDT (-6 UTC) | CDT (-5 UTC) | EDT (-4 UTC) |
| --- | --- | --- | --- | --- |
| Start penumbral (P1) | 1:55 a.m. | 2:55 a.m. | 3:55 a.m. | 4:55 a.m. |
| Start umbral (U1) | 3:17 a.m. | 4:17 a.m. | 5:17 a.m. | 6:17 a.m. |
| Greatest eclipse | 4:38 a.m. | 5:38 a.m. | 6:38 a.m. | Set |
| End umbra (U4) | 6:00 a.m. | Set | Set | Set |
| End penumbral (P4) | Set | Set | Set | Set |
Question:
What is the time for PDT when CDT is 6:38 a.m.?
Answer:
4:38 a.m.