I have a vector with timestamps as following:

```
1521753105.031429052352905
1521753105.081429004669189
1521753105.131428956985474
1521753105.181428909301758
1521753105.231429100036621
1521753105.281429052352905
1521753105.331429004669189
1521753105.381428956985474
1521753105.431428909301758
1521753105.481429100036621
1521753105.531429052352905
1521753105.581429004669189

```

The current time is:

```
1521753105.231428861618042

```

which is in between the 4th and 5th values.

[![The Values lies between two values](https://i.stack.imgur.com/Khq3D.jpg)](https://i.stack.imgur.com/Khq3D.jpg)

How to determine the lower and upper index to the current time?