Improved function for "earth" kernel

[laspsandoval]

Summary

Extract this to a separate function that all three components can call instead of having duplicated code.

Line 715 in file_validation.py

if len(components["start_date"]) == 8:
components["start_date"] = datetime.strptime(
components["start_date"], "%Y%m%d"
)
else:
components["start_date"] = datetime.strptime(
components["start_date"], "%y%m%d"