Resolve Timeline Scale Issues

Are Preceden Timelines Drawn to Scale?

Yes. Preceden positions every event by its dates rather than by its place in a list, and the same amount of time maps to the same number of pixels everywhere on the timeline. An event lasting three months is drawn three times as wide as a one-month event beside it, and the gap between two events is proportional to the time between them.

Two things are worth knowing about how that works in practice:

The axis can extend past your last event. Preceden widens the date range it displays so that long event names fit, which means the timeline sometimes covers more time than your events do. The proportions within it are unaffected. Appearance Settings - Scale explains how to bring the axis back in.
Very brief events stay visible. An event too short to fill a whole pixel at the current scale is still drawn one pixel wide instead of vanishing, and an event with no end date is marked with an icon at its point on the axis rather than a bar.

If you've zoomed into a date range, events that begin before it or end after it are drawn out to the edge of the range you're viewing.

The Timeline Scale Notice

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

The notice reading Your timeline cannot be viewed at this scale, above a link to have Preceden pick the best scale

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

A single Project event spanning all of 2017, viewed at the months scale

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:

The same timeline at the days scale, squashed into hundreds of unreadable axis labels

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:

The same timeline at the 50 Millennia scale, where the event shrinks to a sliver beside a mostly empty axis

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:

The same notice with the Have Preceden determine the best scale link outlined in red

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.