Resolve Timeline Scale Issues
If you manually adjust your timeline's scale settings, you may occasionally see the following notice:

To understand why this happens, imagine a timeline with a single event that spans one year, from Jan 1, 2017 through Dec 31, 2017:

By default, Preceden works out the best scale for you. At the months scale, this timeline shows 14 time periods: 12 for the event, plus one on each side for padding.
What happens if you set the scale to days instead? Rather than 14 time periods, Preceden would have to draw 365, plus one on each side for 367 total:

With that many time periods the timeline winds up squashed, and none of the axis labels are readable.
Rather than render an unreadable timeline, Preceden catches the situation and displays the "Your timeline cannot be viewed at this scale" notice.
Picking a scale of 50 Millennia causes the opposite problem. Now there are too few time periods rather than too many:

Preceden catches this case too, and displays the same notice.
Resolving Scale Issues
There are a few things you can try if you see this notice:
1) Click the Have Preceden determine the best scale link below the scale notice:

This switches your timeline back to automatic scaling, which resolves the notice in most cases. It also sets the Date Range back to Display all events, so if you had zoomed into part of your timeline, you'll see the whole thing again.
2) Click Appearance, select Scale, then set Units to Automatically optimize.
This also switches the timeline back to automatic scaling, but it leaves your Date Range setting alone. Use it if you've zoomed into a specific date range and want to keep it.
3) If it's turned on, uncheck Display a line on today's date, found under Appearance > Axis > Options.
That setting forces the timeline to reach today's date, which causes trouble when your events sit far in the past. For example, if your events span 1990 through 1991 and the scale is set to quarters, turning it on stretches the timeline from two years to more than 30. Thirty years of quarters is over 100 time periods, well past the 40 that Preceden will draw when you choose the units yourself.
In rare cases Preceden can't display a timeline even with automatic scaling and date ranges. We've only seen this when events span several hundred thousand years, and even then the timeline usually renders without issues.
If the notice sticks around no matter what you try, or you believe your timeline should be viewable at a scale that isn't working, email us at [email protected] and we'd be happy to figure out the cause.