FULL PRODUCT VERSION :
java version "9"
Java(TM) SE Runtime Environment (build 9+181)
Java HotSpot(TM) 64-Bit Server VM (build 9+181, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 10.0.15063]

EXTRA RELEVANT SYSTEM CONFIGURATION :
jnlp file hosted by IIS server

A DESCRIPTION OF THE PROBLEM :
jnlp file has href="myjnlp.jnlp" as attribute in jnlp element:
<jnlp spec="1.0+" codebase="http://myserver/myapp" href="myjnlp.jnlp">
This produces an invalid header to request the file from the server.

REGRESSION. Last worked in version 8u144

ADDITIONAL REGRESSION INFORMATION:
java version "1.8.0_144"
Java(TM) SE Runtime Environment (build 1.8.0_144-b01)
Java HotSpot(TM) 64-Bit Server VM (build 25.144-b01, mixed mode)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Create a JNLP file with the href attribute. Try to run the jnlp file.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
JNLP file is retrieved by Java regardless of browser download.
ACTUAL -
The following header line was captured being sent to the server:
If-Modified-Since: Sat, 04 Jan 3117231 04:22:24 GMT\r\n

Note the year is incorrect and causes the web server to return 400, Bad Request.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
Web server rejects request because of bad header.

REPRODUCIBILITY :
This bug can be reproduced always.

CUSTOMER SUBMITTED WORKAROUND :
Remove href from JNLP file (but can only do this if I own the web server).