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[tor-commits] [torspec/master] prop224: Time periods now start at 12:00UTC and last 24 hours.
commit 14dd07742afef46baf5b597b09a3d7e431a55f7a
Author: George Kadianakis <desnacked@xxxxxxxxxx>
Date: Wed Apr 13 14:37:21 2016 +0300
prop224: Time periods now start at 12:00UTC and last 24 hours.
---
proposals/224-rend-spec-ng.txt | 31 +++++++++++++++++++------------
1 file changed, 19 insertions(+), 12 deletions(-)
diff --git a/proposals/224-rend-spec-ng.txt b/proposals/224-rend-spec-ng.txt
index a3fb40b..e270f1d 100644
--- a/proposals/224-rend-spec-ng.txt
+++ b/proposals/224-rend-spec-ng.txt
@@ -609,18 +609,25 @@ Status: Draft
The length of a "time period" is controlled by the consensus
parameter 'hsdir-interval', and is a number of minutes between 30 and
- 14400 (10 days). The default time period length is 1500 (one day plus
- one hour).
-
- Time periods start with the Unix epoch (Jan 1, 1970), and are
- computed by taking the number of whole minutes since the epoch and
- dividing by the time period. So if the current time is 2013-11-12
- 13:44:32 UTC, making the seconds since the epoch 1384281872, the
- number of minutes since the epoch is 23071364. If the current time
- period length is 1500 (the default), then the current time period
- number is 15380. It began 15380*1500*60 seconds after the epoch at
- 2013-11-11 20:00:00 UTC, and will end at (15380+1)*1500*60 seconds
- after the epoch at 2013-11-12 21:00:00 UTC.
+ 14400 (10 days). The default time period length is 1440 (one day).
+
+ Time periods start at the Unix epoch (Jan 1, 1970), and are computed by
+ taking the number of minutes since the epoch and dividing by the time
+ period. However, we want our time periods to start at 12:00UTC every day, so
+ we subtract a "rotation time offset" of 12*60 minutes from the number of
+ minutes since the epoch, before dividing by the time period (effectively
+ making "our" epoch start at Jan 1, 1970 12:00UTC).
+
+ Example: If the current time is 2016-04-13 11:15:01 UTC, making the seconds
+ since the epoch 1460546101, and the number of minutes since the epoch
+ 24342435. We then subtract the "rotation time offset" of 12*60 minutes from
+ the minutes since the epoch, to get 24341715. If the current time period
+ length is 1440 minutes, by doing the division we see that we are currently
+ in time period number 16903.
+
+ Specifically, time period #16903 began 16903*1440*60 + (12*60*60) seconds
+ after the epoch at 2016-04-12 12:00 UTC, and ended at (16904+1)*1500*60 +
+ (12*60*60) seconds after the epoch at 2016-04-13 12:00 UTC.
2.2.2. Overlapping time periods to avoid thundering herds [TIME-OVERLAP]
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