# Date ranges, date basis, and your school's time zone

> Every reporting window is measured on your school's clock, and every report states which date the window applies to. Set the time zone once, then read the caption on each report.

Source: https://www.aerscheduler.com/docs/reports/date-ranges-and-time-zones
Section: Reports and analytics. For: Owners, Admins, Dispatchers, Technicians.

Set the school's time zone once in `Settings → Organization` (web console), then read the caption under
each report's date picker. Those two things settle almost every argument about a report's dates.

## Set the school's time zone

**Who can do this:** Owners, Admins

1. **Open Settings, Organization**

   `Settings → Organization` (web console).

2. **Set the time zone on the time zone card**

   Pick the zone the field is in, not the zone you happen to be sitting in.

![Settings, Organization](https://www.aerscheduler.com/docs/settings-org-timezone.png)

From then on, everything below is measured on the school's clock:

- Every report window, so "Last 30 days" means thirty of the school's days.
- Every dashboard tile's window.
- The day boundaries of a comparison period.
- The dates in a CSV export's file name.
- The hour a scheduled report goes out, so "7am" means 7am at the field.

## What happens when it is not set

The setting starts out unset, and reports still work. They just fall back.

| Situation                                       | What the window is measured on              |
| ----------------------------------------------- | ------------------------------------------- |
| Organization time zone set                      | The school's zone                           |
| Not set, somebody reading a report in a browser | That reader's own browser zone              |
| Not set, a scheduled report sending             | UTC, because a send has no browser attached |

> **Careful:** With no organization zone, two people in different zones can legitimately see slightly different totals for the
> same "Last 30 days" on the same report. Nothing is broken and neither of them is wrong. Set the zone and the
> disagreement goes away.

## The named ranges, and what each one means

Reports and the dashboard offer different presets, which surprises people who go looking for one on the other.

| Where                  | Presets                                                                                          |
| ---------------------- | ------------------------------------------------------------------------------------------------ |
| A report's date picker | Last 7 days, Last 30 days, Last 90 days, Last 12 months                                          |
| The Overview dashboard | Last 7 days, Last 30 days, Last 90 days, Month to date, Year to date, Next 30 days, Next 90 days |

On a report you can also set your own start and end dates.

> **Note:** A saved view stores whatever window was on screen as fixed dates, presets included. "Last 30 days" is resolved when
> you save, so re-applying the view a month later restores that same month, not the last 30 days from today. See
> [Save a report as a view](https://www.aerscheduler.com/docs/reports/save-a-report-view).

## Date basis: which date the range applies to

Under the date picker on every report there is a small caption reading "by" and then a date, such as "by the date
the invoice was raised" or "by the date of the flight".

That caption is the answer to most reporting questions people email about. Your range does not apply to reports in
general, it applies to that specific date.

| Report                                                        | The date the range applies to                                       |
| ------------------------------------------------------------- | ------------------------------------------------------------------- |
| Revenue                                                       | The date the invoice was raised                                     |
| Payments received                                             | The date the invoice was paid                                       |
| Accounts receivable                                           | As of the end of the range (who owes now; the start date is unused) |
| Document expirations, Pilot currency, Endorsement expirations | The expiry date                                                     |
| Maintenance due                                               | The date the reminder was raised, not when it comes due             |

![Revenue and Payments received over the same window](https://www.aerscheduler.com/docs/revenue-vs-payments.png)

> **Careful:** An invoice raised in June and paid in August is June's revenue and August's cash. Revenue and Payments received
> will therefore never agree over the same window at a school where anybody pays late, and both reports are correct.

The caption on the report is always authoritative. Read it before you reconcile two numbers against each other. See
[Report numbers that look wrong](https://www.aerscheduler.com/docs/reports/numbers-dont-match).

## Why expiry reports open on the next 90 days

Document expirations, Pilot currency and Endorsement expirations all window on the expiry date, so they open on the
**next** 90 days rather than the last 30.

Every other report looks backwards, which is exactly why this catches people. Opening a compliance report on the
last 30 days would list what has already lapsed, which is the opposite of what you asked. To see what has already
lapsed, set the range backwards yourself.

> **Note:** A document, currency or endorsement with no expiry date on it never appears on these reports at all. It has no date
> to match a window, so it is missing rather than listed blank.

## Comparison periods: previous period and last year

The Overview dashboard offers "vs previous period", "vs last year" and "No comparison". They are not
interchangeable.

| Comparison         | What it measures against                               |
| ------------------ | ------------------------------------------------------ |
| vs previous period | The same number of days immediately before this window |
| vs last year       | The same calendar dates a year ago                     |

Use "vs last year" when the season matters, which for a flight school is most of the year. "Previous period" is a
strict day count, so comparing a 28 day February against the 28 days before it rarely answers the question you had
in mind.

> **Note:** A number card shows no percentage change when the previous period was zero. Going from 0 to 40 is not a meaningful
> percentage, so the card prints nothing rather than something misleading. When a comparison ran but produced no
> baseline, the card reads "No comparison".

## Scheduled reports ignore the saved view's dates

A schedule points at a saved view, but it does not use that view's window. The cadence decides.

| How often   | What each email covers            |
| ----------- | --------------------------------- |
| Every day   | Yesterday                         |
| Every week  | The seven days ending yesterday   |
| Every month | The whole previous calendar month |

That is deliberate: consecutive emails are meant to tile exactly, with no gaps and no days counted twice. Save a
view over 1 to 31 July, schedule it weekly, and you get last week every week. See
[Email a report on a schedule](https://www.aerscheduler.com/docs/reports/email-a-report-on-a-schedule).

Those windows are measured on the school's clock, and a scheduled send falls straight through to UTC when no
organization zone is set, because there is no browser to fall back to. That is the strongest reason to set the
zone.

## Where else time zones matter

Reporting is not the only place a clock decides something. Booking times, ramp times and what "today" means on the
schedule are covered separately, in
[Airport time and time zones](https://www.aerscheduler.com/docs/scheduling/airport-time-and-time-zones).