sudo apt-get install libemail-outlook-message-perl libemail-sender-perl
from a command line. Use
msgconvert *.msg
to convert every file in a directory at once. MSGConvert will produce copies of your .msg-files with the suffix .msg.eml
JSON itself does not specify how dates should be represented, but JavaScript does.
You should use the format emitted by Date's toJSON method:
2012-04-23T18:25:43.511Z