[time-duration] Implement time-duration concept and time-keeper concept exercise

concepts/time-duration/.meta/config.json

@@ -0,0 +1,7 @@
+{
+  "blurb": "Learn how concept time and duration is implemented in Go.",
+  "authors": [
+    "thibault2705"
+  ],
+  "contributors": []
+}

concepts/time-duration/about.md

@@ -0,0 +1,94 @@
+# About
+
+In Go, time-based calculations are handled using the [`time`][time-package]  package.  
+Two key types used in this exercise are:
+
+- [`time.Time`][time]: represents a specific moment in time (a timestamp)
+- [`time.Duration`][duration]: represents the amount of time elapsed between two moments
+
+---
+
+## `time.Time` vs `time.Duration`
+
+A `time.Time` represents an absolute point in time, such as:
+
+```go
+t := time.Now()
+```
+
+A `time.Duration` represents the difference between two points in time:
+```go
+start := time.Now()
+end := start.Add(5 * time.Minute)
+
+duration := end.Sub(start) // => 5m0s
+```
+
+In short:
+- `time.Time` → “when something happens”
+- `time.Duration` → “how long it lasts”
+
+## Measuring Time with `time.Since`
+To measure how long something takes (e.g., execution time), you can use `time.Since`[since]
+```go
+start := time.Now()
+
+// some work here
+
+elapsed := time.Since(start)
+fmt.Println(elapsed)
+```
+
+## Adding and Subtracting Time
+You can manipulate timestamps using:
+- [`Time.Add()`][add] → add or subtract a duration
+- [`Time.Sub()`][sub] → calculate the difference between two times
+
+## Time Units
+Go provides built-in constants for time units:
+
+| Unit        | Constant             |
+| ----------- |----------------------|
+|Nanosecond   | `time.Nanosecond`    |
+|Microsecond  | `time.Microsecond `  |
+|Millisecond  | `time.Millisecond`   |
+|Second       | `time.Second`        |
+|Minute       | `time.Minute`        |
+|Hour         | `time.Hour`          |
+
+You can combine them to build durations:
+```go
+d := 1*time.Hour + 5*time.Minute + 19*time.Second + 234*time.Millisecond
+```
+
+You can also perform calculations:
+```go
+seconds := d.Seconds()   // float64
+minutes := d.Minutes()
+```
+
+## Working with Durations
+Durations can be:
+- Added to a `time.Time`
+- Subtracted from a `time.Time`
+- Compared or converted to different units
+
+```go
+start := time.Now()
+finish := start.Add(30 * time.Second)
+
+duration := finish.Sub(start) // => 30s
+```
+
+## Other resources
+- [Go by Example: Time](https://gobyexample.com/time)
+- [Go by Example: Time Formatting / Parsing](https://gobyexample.com/time-formatting-parsing)
+
+[time-package]: https://pkg.go.dev/time
+[time]: https://pkg.go.dev/time#Time
+[duration]: https://pkg.go.dev/time#Duration
+[since]: https://pkg.go.dev/time#Since
+[add]: https://pkg.go.dev/time#Time.Add
+[sub]: https://pkg.go.dev/time#Time.Sub
+[now]: https://pkg.go.dev/time#Now
+

concepts/time-duration/introduction.md

@@ -0,0 +1,94 @@
+# Introduction
+
+In Go, time-based calculations are handled using the [`time`][time-package]  package.  
+Two key types used in this exercise are:
+
+- [`time.Time`][time]: represents a specific moment in time (a timestamp)
+- [`time.Duration`][duration]: represents the amount of time elapsed between two moments
+
+---
+
+## `time.Time` vs `time.Duration`
+
+A `time.Time` represents an absolute point in time, such as:
+
+```go
+t := time.Now()
+```
+
+A `time.Duration` represents the difference between two points in time:
+```go
+start := time.Now()
+end := start.Add(5 * time.Minute)
+
+duration := end.Sub(start) // => 5m0s
+```
+
+In short:
+- `time.Time` → “when something happens”
+- `time.Duration` → “how long it lasts”
+
+## Measuring Time with `time.Since`
+To measure how long something takes (e.g., execution time), you can use `time.Since`[since]
+```go
+start := time.Now()
+
+// some work here
+
+elapsed := time.Since(start)
+fmt.Println(elapsed)
+```
+
+## Adding and Subtracting Time
+You can manipulate timestamps using:
+- [`Time.Add()`][add] → add or subtract a duration
+- [`Time.Sub()`][sub] → calculate the difference between two times
+
+## Time Units
+Go provides built-in constants for time units:
+
+| Unit        | Constant             |
+| ----------- |----------------------|
+|Nanosecond   | `time.Nanosecond`    |
+|Microsecond  | `time.Microsecond `  |
+|Millisecond  | `time.Millisecond`   |
+|Second       | `time.Second`        |
+|Minute       | `time.Minute`        |
+|Hour         | `time.Hour`          |
+
+You can combine them to build durations:
+```go
+d := 1*time.Hour + 5*time.Minute + 19*time.Second + 234*time.Millisecond
+```
+
+You can also perform calculations:
+```go
+seconds := d.Seconds()   // float64
+minutes := d.Minutes()
+```
+
+## Working with Durations
+Durations can be:
+- Added to a `time.Time`
+- Subtracted from a `time.Time`
+- Compared or converted to different units
+
+```go
+start := time.Now()
+finish := start.Add(30 * time.Second)
+
+duration := finish.Sub(start) // => 30s
+```
+
+## Other resources
+- [Go by Example: Time](https://gobyexample.com/time)
+- [Go by Example: Time Formatting / Parsing](https://gobyexample.com/time-formatting-parsing)
+
+[time-package]: https://pkg.go.dev/time
+[time]: https://pkg.go.dev/time#Time
+[duration]: https://pkg.go.dev/time#Duration
+[since]: https://pkg.go.dev/time#Since
+[add]: https://pkg.go.dev/time#Time.Add
+[sub]: https://pkg.go.dev/time#Time.Sub
+[now]: https://pkg.go.dev/time#Now
+

concepts/time-duration/links.json

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+[
+  {
+    "url": "https://pkg.go.dev/time",
+    "description": "Go packages: time package"
+  },
+  {
+    "url": "https://pkg.go.dev/time#Time",
+    "description": "Go packages: time.Time type"
+  },
+  {
+    "url": "https://pkg.go.dev/time#Duration",
+    "description": "Go packages: time.Duration type"
+  },
+  {
+    "url": "https://pkg.go.dev/time#Since",
+    "description": "Go packages: time.Since function"
+  },
+  {
+    "url": "https://pkg.go.dev/time#Time.Add",
+    "description": "Go packages: time.Time.Add method"
+  },
+  {
+    "url": "https://pkg.go.dev/time#Time.Sub",
+    "description": "Go packages: time.Time.Sub method"
+  },
+  {
+    "url": "https://pkg.go.dev/time#Now",
+    "description": "Go packages: time.Now function"
+  },
+  {
+    "url": "https://gobyexample.com/time",
+    "description": "Go by Example: Time"
+  },
+  {
+    "url": "https://gobyexample.com/time-formatting-parsing",
+    "description": "Go by Example: Time Formatting / Parsing"
+  }
+]

config.json

@@ -428,6 +428,17 @@
           "methods",
           "structs"
         ]
+      },
+      {
+        "slug": "time-keeper",
+        "name": "Time Keeper",
+        "uuid": "82abf57d-891b-484f-b4d8-309e1486a6f5",
+        "concepts": [
+          "time-duration"
+        ],
+        "prerequisites": [
+          "time"
+        ]
       }
     ],
     "practice": [
@@ -2530,6 +2541,11 @@
       "uuid": "f22b0e85-4d86-4ecf-9415-ea27c93ebcd6",
       "slug": "error-wrapping",
       "name": "Error Wrapping"
+    },
+    {
+      "uuid": "32ee0ee7-7191-4d21-aa8b-f912cae21ca7",
+      "slug": "time-duration",
+      "name": "Time Duration"
     }
   ],
   "key_features": [

exercises/concept/time-keeper/.docs/hints.md

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+# Hints
+
+## 1. Calculate Duration
+
+Think about how to measure the time between two moments.  
+Go provides a built-in way to compare timestamps directly.
+
+---
+
+## 2. Handle Different Time Zones
+
+You don’t need to manually adjust for time zones.  
+Focus on comparing the two timestamps as they are.
+
+---
+
+## 3. Parse Recorded Times
+
+The input follows a structured format with hours, minutes, and seconds.  
+Look for a standard library function that can interpret duration strings.
+
+---
+
+## 4. Correct Start Time
+
+You need to adjust a timestamp by moving it backward in time.  
+Consider how to shift a time value using a duration.
+
+---
+
+## 5. Filter Valid Detections
+
+First determine how much time has passed since the start.  
+Then check whether that elapsed time falls within a given range.
+
+---
+
+## 6. Format Leaderboard Output
+
+You need to display:
+- the runner’s total time
+- the difference compared to the leader
+
+Think about:
+- how to convert a duration to a readable string
+- how to express the difference in seconds with precision
+
+---
+
+## General Advice
+
+- Prefer built-in time utilities instead of manual calculations
+- Be careful with boundaries when checking ranges
+- Keep your solution simple and precise — timing systems must be reliable