Convert hex-timestamp back

I often see timestamp values in a form-field written in hex:

<input type="hidden" name="timestamp" value="b1a38fee9509c100228be1dc5d379cd9">

How can I calculate them back to something readable? First I thought about making Byte-Chunks and then calculating them into decimals, but that didn't make much sence to me:

b1   a3  8f  ee  95  09  c1  00  22  8b  e1  dc  5d  37  9c  d9
177 163 143 238 149 009 193 000 034 139 225 220 093 055 156 217

Thank you