How long are your cycles and when is your ovulation date typically?

I've a newbie to this.  I've been using the opks recently.  I'm on the second day of my fertility window and I'm not even getting a faint line.  I tested one cycle before, but missed a day or two that cycle, and I did get faint lines, but no positives.  My cycle is usually 29-30 days long, but last month it was 34 days (and I was really disappointed).  I'm on day 14 now.  I just kind of want to get a feel for when ovulation occurs for different cycles and people.