Add proper README

README.md

@@ -1,2 +1,30 @@
 # time.txt
 
+Simple plain-text time tracking.
+
+The Python script `tx` provides short-hands for accessing and reading a `time.txt` file, as described below.
+
+## Usage
+
+Create a new `time.txt` file at the current location: `tx create`
+
+Add a time entry: `tx add 01:00 Totally productive work`
+
+View the total unbilled time: `tx total` or simply `tx`
+
+Remove time which was billed: `tx bill 05:00 Fee note for this month`
+
+## Format
+
+The `time.txt` file is written in the following format:
+
+```
+2020-08-12 01:00 Work on Task 1
+2020-08-12 03:00 Work on Task 2
+2020-08-16 05:00 Finish Task 2
+2020-08-31 -08:00 Fee note for August
+```
+
+With this file, the total amount of (unbilled) hours is 01:00.
+
+All `tx` commands are simply short-hands for accessing and reading this file comfortably. It can be edited manually at any time.