Let's consider an aged partner balance with a period of 30 days as of
2019-02-08. The specific dates used in the report are:
``` python
bisou = datetime.strptime('2019-02-08', "%Y-%m-%d").date()
for x in [0, 1, 30, 31, 60, 61, 90, 91, 120, 121]:
print(x, bisou + relativedelta(days=-x))
0 2019-02-08
1 2019-02-07
30 2019-01-09
31 2019-01-08
60 2018-12-10
61 2018-12-09
90 2018-11-10
91 2018-11-09
120 2018-10-11
121 2018-10-10
```
However, the current periods generated are incorrect:
```
{'name': '0-30', 'stop': '2019-02-08', 'start': '2019-01-09'}
{'name': '30-60', 'stop': '2019-01-08', 'start': '2018-12-09'}
{'name': '60-90', 'stop': '2018-12-08', 'start': '2018-11-08'}
{'name': '90-120', 'stop': '2018-11-07', 'start': '2018-10-08'}
{'name': '+120', 'stop': '2018-10-07', 'start': False}
```
There is a clear inconsistency between the name of the period and the
date used. Moreover, the name is misleading: 0-30 includes the -0 date,
while 30-60 doesn't include the -30 date.
After the fix, the name and the periods are consistent. We also change
the first period to 1-30 since including 0 would mean to include amounts
which are not due yet.
```
{'name': '1-30', 'stop': '2019-02-07', 'start': '2019-01-09'}
{'name': '31-60', 'stop': '2019-01-08', 'start': '2018-12-10'}
{'name': '61-90', 'stop': '2018-12-09', 'start': '2018-11-10'}
{'name': '91-120', 'stop': '2018-11-09', 'start': '2018-10-11'}
{'name': '+120', 'stop': '2018-10-10', 'start': False}
```
opw-1886633
closesodoo/odoo#27294
Nicolas Martinelli
3c4f853365