0 safe days should mean the emergency day is today, not tomorrow.
Even though I have been using Beeminder for a few months, I still get confused by the number of safety days. It would make more sense to me if having 0 safe days meant I need to enter data by tonight. (Right now, it means that I need to enter data by tomorrow night.)
This would be a big change, in the sense that it would initially confuse some early users. But I think it would make more sense for new users, that it would not take long for early users to get used to it, and that it is still early enough in Beeminder's history for such changes to be made.
maybe instead of showing the -1 on the graph as number of safe days left, it could say "eep!" or something like that. :-)
"Time to derailment" would be awesome. I guess this would be doable if/when you switch to HTML5 for the graphs?
I think the concept of safe days is much harder grasp than "time to derailment". Time to derailment is effectively a countdown and intuitively clear.
I really like how the android app shows hours to derailment if the safe days is -1 (rather than showing -1 safe days). It promotes a sense of urgency. Minus numbers are not easy for our minds to grasp and therefore don't seem to promote that.
Although updating the graph with hours is problematic, it could be displayed on the goal stats.
Updating the graphs with hours might be tricky. So if 0 safe days means the emergency day, and you think about it in terms of derailment days, then 0 safe days would then mean less than 24 hours to derailment. 1 safe days would then mean 1 more day before derailment day (e.g. derailment at the end of +1 days).
If it is Monday, and I have 5 "safe days/5 days to derailment day"), then I derail at the end of Saturday. This makes sense. And I think this is an improvement on having safe days and emergency days as separate constructs - you just have the concept of derailment days - days before derailment and then derailment day. But then safe days loses its meaning somewhat, which has some drawbacks.
And RIP for off the road is also nicer than -2 safe days!
Ok, enough rationalizing the status quo. You're totally right, Robin. Instead of justifying an esoteric definition of "safe days" we need to just give a "time to derailment".
Shorter version of the counterargument: an "emergency" day doesn't count as a "safe" day. And since we think of it as a safety *buffer* we're counting safe days starting tomorrow.
Wrong lane ==> no safety buffer.
1. The true yellow brick road is the centerline so if you're in the wrong lane you're sort of in arrears already.
2. If you're in the wrong lane then there are no (zero) more safe days -- tomorrow you'll be off the road. (Yes, tomorrow you'll only *start* off the road and can still get back on by the end of the day, but you really shouldn't be letting that happen anyway!)
3. Think of it as "how many more days can I do nothing?"
4. It's arguably going to be confusing either way, so better to err on the side of caution. If you misinterpret the number of safe days as defined now, then you'll be a day ahead of schedule. If we do it your way then misinterpreting = derailment!
I do see your point though and if the above doesn't convince you, let me know! It does seem inelegant to ever say "-1 safe days".
Now I'm wondering if a better solution would be to always say exactly how many days or hours/minutes/seconds remain till derailment. That's tough for now with our static graph images, but that may be the eventual answer. (Thanks for the help in thinking this through!)