DOTM and DOT are document templates from Microsoft Word, albeit from different versions of the software and also with the difference that .dotm file allow macros.
Nonetheless you can freely re-save templates even to the previous version, but keep in mind this will not only disable the macros, but also remove any features and formatting not applicable to the older .dot files. Except for MS Word, this should be also possible with any alternative word processing tool that supports MS Word formats.