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:
| Unit | Type | Net Power | Total Power | Finish construction |
| --- | --- | --- | --- | --- |
| Greifswald - 1 (KGR 1) | WWER-440/230 | 408 MW | 440 MW | 17.12.1973 |
| Greifswald - 2 (KGR 2) | WWER-440/230 | 408 MW | 440 MW | 23.12.1974 |
| Greifswald - 3 (KGR 3) | WWER-440/230 | 408 MW | 440 MW | 24.10.1977 |
| Greifswald - 4 (KGR 4) | WWER-440/230 | 408 MW | 440 MW | 03.09.1979 |
| Greifswald - 5 (KGR 5) | WWER-440/213 | 408 MW | 440 MW | 24.04.1989 |
| Greifswald - 6 (KGR 6) | WWER-440/213 | 408 MW | 440 MW | Finished, never operated |
| Greifswald - 7 (KGR 7) | WWER-440/213 | 408 MW | 440 MW | Canceled |
| Greifswald - 8 (KGR 8) | WWER-440/213 | 408 MW | 440 MW | Canceled |
Question:
What was the date that construction was finished when the unit was greifswald - 4 (kgr 4)?
Answer:
3091979.0