Fix broken link about lunar day

core/datetime/datetime.ipynb

@@ -351,7 +351,7 @@
     "\n",
     "In these examples, we will look at current data pertaining to coastal tides during a [tropical cyclone storm surge](http://www.nhc.noaa.gov/surge/).\n",
     "\n",
-    "The [lunar day](http://oceanservice.noaa.gov/education/kits/tides/media/supp_tide05.html) is 24 hours and 50 minutes; there are two low tides and two high tides in that time duration. If we know the time of the current high tide, we can easily calculate the occurrence of the next low and high tides by using the [timedelta class](https://docs.python.org/3/library/datetime.html#timedelta-objects). (In reality, the *exact time* of tides is influenced by local coastal effects, in addition to the laws of celestial mechanics, but we will ignore that fact for this exercise.)\n",
+    "The [lunar day](https://tidesandcurrents.noaa.gov/glossary.html#lunarday) is 24 hours and 50 minutes; there are two low tides and two high tides in that time duration. If we know the time of the current high tide, we can easily calculate the occurrence of the next low and high tides by using the [timedelta class](https://docs.python.org/3/library/datetime.html#timedelta-objects). (In reality, the *exact time* of tides is influenced by local coastal effects, in addition to the laws of celestial mechanics, but we will ignore that fact for this exercise.)\n",
     "\n",
     "The `timedelta` class is initialized by supplying time duration, usually supplied with [keyword arguments](https://docs.python.org/3/glossary.html#term-argument), to clearly express the length of time. The `timedelta` class allows you to perform arithmetic with dates and times using standard operators (i.e., `+`, `-`, `*`, `/`).  You can use these operators with a `timedelta` object, and either another `timedelta` object, a datetime object, or a numeric literal, to obtain objects representing new dates and times.\n",
     "\n",
@@ -554,7 +554,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.10.9"
+   "version": "3.11.9"
   }
  },
  "nbformat": 4,