> For the complete documentation index, see [llms.txt](https://support.who-umc.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://support.who-umc.org/vigilyze/algorithms-used-in-vigilyze/time-computations.md).

# Time computations

Age, Reaction duration, Drug treatment duration and Time-To-Onset

These values are considered durations and are all calculated according to the same principles. If the actual value is not reported, a calculated duration from reported dates are shown.’

| Duration                | Start date        | Stop date           |
| ----------------------- | ----------------- | ------------------- |
| Patient age             | PatientBirthDate  | ReactionStartDate\* |
| Reaction duration       | ReactionStartDate | ReactionEndDate     |
| Drug treatment duration | DrugStartDate     | DrugEndDate         |
| Time-To-Onset           | DrugStartDate     | ReactionStartDate   |

\*When several reactions with different start dates are reported within the same case, the
\
earliest date is used.

Each date is given a min and a max value (down to minute), see examples below:

| Date (reported) | Date min         | Date max         |
| --------------- | ---------------- | ---------------- |
| 2000            | 2000-01-01 00:00 | 2000-12-31 23:59 |
| 200001          | 2000-01-01 00:00 | 2000-01-31 23:59 |
| 20000101        | 2000-01-01 00:00 | 2000-01-01 23:59 |
| 2000010113      | 2000-01-01 13:00 | 2000-01-01 13:59 |
| 200001011334    | 2000-01-01 13:34 | 2000-01-01 13:34 |

Duration is calculated out of the min and the max dates and each duration is given a min, max
\
and mean value.

Duration min is set to the time span between the highest possible start date and the lowest
\
possible stop date (e.g. for Patient age it is ReactionStartDate min – PatientBirthDate max)
\
Duration max is set to the time span between the lowest possible start date and the highest possible stop date (e.g. for Patient age it is ReactionStartDate max – PatientBirthDate min)
\
Duration mean is set to (Duration min + Duration max) /2.

Durations are always rounded to nearest integer, except age which is rounded down. Duration
\
mean is shown in VigiLyze, see examples below:

| Start date - Stop date    | Duration min | Duration max |             |
| ------------------------- | ------------ | ------------ | ----------- |
| 200406-2006               | 1.5 years    | 2.6 years    | 2 years     |
| 20050506 – 2011           | 5.7 years    | 6.7 years    | 6 years     |
| 20130617-201309           | 2.5 months   | 3.4 months   | <p>3 months |
| <br>2 months (if age)</p> |              |              |             |
| 19840108-19840111         | 2 days       | 4 days       | 3 days      |
| 19840108-19840108         | -1 day       | 1 day        | 0 days      |
| 20090511-20090530         | 18 days      | 20 days      | 19 days     |
| 201103-2011               | 3 months     | 10 months    | -\*         |
| 2005-2005                 | -12 months   | 12 months    | -\*         |
| 200105-200105             | -31 days     | 31 days      | -\*         |
| 20040903-200409           | -3 days      | 28 days      | -\*         |

\*If the uncertainty is high, i.e. difference between max and mean duration is more than 1.5,
\
no duration is shown. This happens with incomplete dates that are close in time.


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