When I run TTF fonts through OpenType Compiler to add OpenType features it sets the Modified and Created dates back to 1 January 1904.
I can open them in FontCreator and enter the correct dates, then save as TTF, renaming as OTF in the process or in Windows Explorer, and all seems to work well.
Are any problems likely to be introduced by doing this? I want the correct dates to show up in MainType4 and in the MS Font Properties Extensions utility.
FCP doesn’t strip the OpenType tables from the font, so unless you change Postscript names, the order of glyphs, or other such, I can’t imagine any problem cropping up.
Are you sure!
I run into emotional problems with OTF fonts which I hesitate to correct because of the OTF ends up as a TTF when saved. If I could simply rename the ttf that would be terrific.
What is included in “or other such” – editing glyphs, changing font names, …?
FontCreator can strip some tables on opening fonts — it depends on the settings in Options, Font, but I have all checkboxes disabled.
Since OpenType features rely on Postscript names, changing those could obviously break some features, but I am not going to do that.
Its the problems that you cannot imagine that I’m worried about. 
Is there a way to test/check the condition of OTF fonts? Freely.
What to you mean by that?
The TrueType Viewer will let you preview OpenType features to see if they work, even if you don’t have InDesign or PagePlus or Word 2010 to test them.
Will try it. Thanks. D
There are two OpenType flavors, TrueType based and PostScript based OpenType. For more background information about this see: What is the difference between TrueType and OpenType?
FontCreator supports one of them. The one based on TrueType outlines. Usually such font files have a .ttf extension, but a .otf extension is valid as well.
If you open a PostScript based OpenType font (prefered extension is .otf), the outlines (CFF) will be converted to TrueType (glyf) outlines, and among that the instructions for hinting are lost.
You can safely open and save a TrueType based OpenType font, but there are several restrictions if the font contains unsupported tables.
First make sure the “Remove” flags are unset, especially “Remove unsupported tables” before opening the font. You can change these flags through the Options window. To see or change these settings, go to the main menu, and open the Tools menu, click Options, and then click the Font tab.
Then you can edit such font, but you will most likely break something within the unsupported tables if you add, remove, or change the order of the glyphs.