why can't .net parse date twine timezone?

.net throws an difference perplexing parse datetime twine format:

fri, 10 oct 2008 00:05:51 cst

convert.todatetime("fri, 10 oct 2008 00:05:51 cst") law an exception:

the twine famous a
current datetime. there unknown
starting during index 26

character 26 apparently being start "cst"

in discerning test, php javascript both parse twine date problem. .net only full destroy there reasonable explanation?

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