What is this encoding and how do you decode it?

[Dmyicgglrhxgi]

I'm working with an XML document and within a certain element that deals with setting date and time ranges I have this string that's some for of encoding:\[code\]<CONTAIN>AQEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAwAnkQAAAAADACeRA</CONTAIN>\[/code\]Does this form of character encoding look familiar to anyone? My first thought was base64 but decoding it as base64 returns garbled text.I'd love to know how this is encoded and how you would decode it.