-Dygraph.WEEKLY = 14;
-Dygraph.MONTHLY = 15;
-Dygraph.QUARTERLY = 16;
-Dygraph.BIANNUAL = 17;
-Dygraph.ANNUAL = 18;
-Dygraph.DECADAL = 19;
-Dygraph.CENTENNIAL = 20;
-Dygraph.NUM_GRANULARITIES = 21;
-
-/** @type {Array.<number>} */
-Dygraph.SHORT_SPACINGS = [];
-Dygraph.SHORT_SPACINGS[Dygraph.SECONDLY] = 1000 * 1;
-Dygraph.SHORT_SPACINGS[Dygraph.TWO_SECONDLY] = 1000 * 2;
-Dygraph.SHORT_SPACINGS[Dygraph.FIVE_SECONDLY] = 1000 * 5;
-Dygraph.SHORT_SPACINGS[Dygraph.TEN_SECONDLY] = 1000 * 10;
-Dygraph.SHORT_SPACINGS[Dygraph.THIRTY_SECONDLY] = 1000 * 30;
-Dygraph.SHORT_SPACINGS[Dygraph.MINUTELY] = 1000 * 60;
-Dygraph.SHORT_SPACINGS[Dygraph.TWO_MINUTELY] = 1000 * 60 * 2;
-Dygraph.SHORT_SPACINGS[Dygraph.FIVE_MINUTELY] = 1000 * 60 * 5;
-Dygraph.SHORT_SPACINGS[Dygraph.TEN_MINUTELY] = 1000 * 60 * 10;
-Dygraph.SHORT_SPACINGS[Dygraph.THIRTY_MINUTELY] = 1000 * 60 * 30;
-Dygraph.SHORT_SPACINGS[Dygraph.HOURLY] = 1000 * 3600;
-Dygraph.SHORT_SPACINGS[Dygraph.TWO_HOURLY] = 1000 * 3600 * 2;
-Dygraph.SHORT_SPACINGS[Dygraph.SIX_HOURLY] = 1000 * 3600 * 6;
-Dygraph.SHORT_SPACINGS[Dygraph.DAILY] = 1000 * 86400;
-Dygraph.SHORT_SPACINGS[Dygraph.WEEKLY] = 1000 * 604800;
+Dygraph.TWO_DAILY = 14;
+Dygraph.WEEKLY = 15;
+Dygraph.MONTHLY = 16;
+Dygraph.QUARTERLY = 17;
+Dygraph.BIANNUAL = 18;
+Dygraph.ANNUAL = 19;
+Dygraph.DECADAL = 20;
+Dygraph.CENTENNIAL = 21;
+Dygraph.NUM_GRANULARITIES = 22;
+
+// Date components enumeration (in the order of the arguments in Date)
+// TODO: make this an @enum
+Dygraph.DATEFIELD_Y = 0;
+Dygraph.DATEFIELD_M = 1;
+Dygraph.DATEFIELD_D = 2;
+Dygraph.DATEFIELD_HH = 3;
+Dygraph.DATEFIELD_MM = 4;
+Dygraph.DATEFIELD_SS = 5;
+Dygraph.DATEFIELD_MS = 6;
+Dygraph.NUM_DATEFIELDS = 7;
+
+
+/**
+ * The value of datefield will start at an even multiple of "step", i.e.
+ * if datefield=SS and step=5 then the first tick will be on a multiple of 5s.
+ *
+ * For granularities <= HOURLY, ticks are generated every `spacing` ms.
+ *
+ * At coarser granularities, ticks are generated by incrementing `datefield` by
+ * `step`. In this case, the `spacing` value is only used to estimate the
+ * number of ticks. It should roughly correspond to the spacing between
+ * adjacent ticks.
+ *
+ * @type {Array.<{datefield:number, step:number, spacing:number}>}
+ */
+Dygraph.TICK_PLACEMENT = [];
+Dygraph.TICK_PLACEMENT[Dygraph.SECONDLY] = {datefield: Dygraph.DATEFIELD_SS, step: 1, spacing: 1000 * 1};
+Dygraph.TICK_PLACEMENT[Dygraph.TWO_SECONDLY] = {datefield: Dygraph.DATEFIELD_SS, step: 2, spacing: 1000 * 2};
+Dygraph.TICK_PLACEMENT[Dygraph.FIVE_SECONDLY] = {datefield: Dygraph.DATEFIELD_SS, step: 5, spacing: 1000 * 5};
+Dygraph.TICK_PLACEMENT[Dygraph.TEN_SECONDLY] = {datefield: Dygraph.DATEFIELD_SS, step: 10, spacing: 1000 * 10};
+Dygraph.TICK_PLACEMENT[Dygraph.THIRTY_SECONDLY] = {datefield: Dygraph.DATEFIELD_SS, step: 30, spacing: 1000 * 30};
+Dygraph.TICK_PLACEMENT[Dygraph.MINUTELY] = {datefield: Dygraph.DATEFIELD_MM, step: 1, spacing: 1000 * 60};
+Dygraph.TICK_PLACEMENT[Dygraph.TWO_MINUTELY] = {datefield: Dygraph.DATEFIELD_MM, step: 2, spacing: 1000 * 60 * 2};
+Dygraph.TICK_PLACEMENT[Dygraph.FIVE_MINUTELY] = {datefield: Dygraph.DATEFIELD_MM, step: 5, spacing: 1000 * 60 * 5};
+Dygraph.TICK_PLACEMENT[Dygraph.TEN_MINUTELY] = {datefield: Dygraph.DATEFIELD_MM, step: 10, spacing: 1000 * 60 * 10};
+Dygraph.TICK_PLACEMENT[Dygraph.THIRTY_MINUTELY] = {datefield: Dygraph.DATEFIELD_MM, step: 30, spacing: 1000 * 60 * 30};
+Dygraph.TICK_PLACEMENT[Dygraph.HOURLY] = {datefield: Dygraph.DATEFIELD_HH, step: 1, spacing: 1000 * 3600};
+Dygraph.TICK_PLACEMENT[Dygraph.TWO_HOURLY] = {datefield: Dygraph.DATEFIELD_HH, step: 2, spacing: 1000 * 3600 * 2};
+Dygraph.TICK_PLACEMENT[Dygraph.SIX_HOURLY] = {datefield: Dygraph.DATEFIELD_HH, step: 6, spacing: 1000 * 3600 * 6};
+Dygraph.TICK_PLACEMENT[Dygraph.DAILY] = {datefield: Dygraph.DATEFIELD_D, step: 1, spacing: 1000 * 86400};
+Dygraph.TICK_PLACEMENT[Dygraph.TWO_DAILY] = {datefield: Dygraph.DATEFIELD_D, step: 2, spacing: 1000 * 86400 * 2};
+Dygraph.TICK_PLACEMENT[Dygraph.WEEKLY] = {datefield: Dygraph.DATEFIELD_D, step: 7, spacing: 1000 * 604800};
+Dygraph.TICK_PLACEMENT[Dygraph.MONTHLY] = {datefield: Dygraph.DATEFIELD_M, step: 1, spacing: 1000 * 7200 * 365.2524}; // 1e3 * 60 * 60 * 24 * 365.2524 / 12
+Dygraph.TICK_PLACEMENT[Dygraph.QUARTERLY] = {datefield: Dygraph.DATEFIELD_M, step: 3, spacing: 1000 * 21600 * 365.2524}; // 1e3 * 60 * 60 * 24 * 365.2524 / 4
+Dygraph.TICK_PLACEMENT[Dygraph.BIANNUAL] = {datefield: Dygraph.DATEFIELD_M, step: 6, spacing: 1000 * 43200 * 365.2524}; // 1e3 * 60 * 60 * 24 * 365.2524 / 2
+Dygraph.TICK_PLACEMENT[Dygraph.ANNUAL] = {datefield: Dygraph.DATEFIELD_Y, step: 1, spacing: 1000 * 86400 * 365.2524}; // 1e3 * 60 * 60 * 24 * 365.2524 * 1
+Dygraph.TICK_PLACEMENT[Dygraph.DECADAL] = {datefield: Dygraph.DATEFIELD_Y, step: 10, spacing: 1000 * 864000 * 365.2524}; // 1e3 * 60 * 60 * 24 * 365.2524 * 10
+Dygraph.TICK_PLACEMENT[Dygraph.CENTENNIAL] = {datefield: Dygraph.DATEFIELD_Y, step: 100, spacing: 1000 * 8640000 * 365.2524}; // 1e3 * 60 * 60 * 24 * 365.2524 * 100
+