There can be three kind of dates indicated on the package of milk (in Japan).
I have never seen the product with product
time.
1) date of production : not milked but processed date
2) date of limit for best by (before opening the package) : less than 3 months from production date
3) date of limit for consumption (before opening the package) : less than 5 days from production date
Refer to
Expiry dates | The Japan Times for details.
One of Japanese milk vendor stated that they indicate 2) for high temperature sterilization or indicate 3) for low temperature sterilization.
賞味期限と消費期限 - 東毛酪農業協同組合 (in Japanese)
As the common sense in Japan, we usually buy high temperature sterilized milk and consume within two or three days after opening the package.