Week 38 is the 20th to the 26th of September and that is the confirmed date that Android version 2.1 (or Eclair as it is also known) for the Xperia X10 series will be released in Spain.
The Spanish division of Sony Ericsson apparently have posted on their Facebook page, as shown above declaring that Eclair will be launched during week 38 and this ties in well with our previously known information that the update would be released in Q3 of this year.