The court may not "arbitrarily or capriciously" modify the provisions for alimony or child support but can do so only after a substantial change is shown to have occurred. Gregory v. Gregory (1964), 52 Ill. App.2d 262, 268, 202 N.E.2d 139. The defendant maintains that the record reflects substantial evidence of a change in circumstances since the decree was entered.

[5] We are satisfied fixed awards of money for child support, alimony, and property settlement draw interest at five percent per annum from date of judgment, or in case of specified periodic payments from the date each such payment becomes due and owing. Code section 535.3; Whittier v. Whittier, supra; Riemenschneider v. Riemenschneider, 239 Iowa 617, 634, 30 N.W.2d 769; Parker v. Parker, 155 Neb. 325, 51 N.W.2d 753, 756; Gregory v. Gregory, 52 Ill. App.2d 262, 202 N.E.2d 139; Shuff v. Fulte, 344 Ill. App. 157, 100 N.E.2d 502; McKay v. McKay, 13 Utah 2d 187, 370 P.2d 358; Howard v. Howard, 142 Cal.App.2d 222, 298 P.2d 48; Bickle v. Bickle, 196 Minn. 392, 265 N.W. 276; Harden v. Harden, 191 Okla. 698, 130 P.2d 311; 47 C.J.S., Interest, section 21, pages 33-35; 27B C.J.S., Divorce, section 377, page 872; 30 Am. Jur., Rev. Ed., Interest, section 24, page 22; and Nelson on Divorce and Annulment, Second Ed., section 14.73.

The court held that expenses related to a second marriage are only of secondary consideration vis-a-vis the obligation owed to a former wife on the question of support. In another earlier case, cited in Berkheimer, the court held that the obligations to a former wife take precedence over the obligations that arise from a subsequent remarriage. ( Gregory v. Gregory (1964), 52 Ill. App.2d 262, 202 N.E.2d 139 (remarriage and birth of child by second marriage does not present, in itself, a change of circumstances sufficient to warrant modification).) The Gregory court specifically stated its reasoning:

There is authority for the broad proposition that a father's obligation to his second family does not present, in itself, a change of circumstances sufficient to warrant modifications of a support order. ( E.g., Gregory v. Gregory (1964), 52 Ill. App.2d 262, 202 N.E.2d 139.) In Gregory, defendant had violated a decree under which he was ordered to pay his former wife alimony and child support for his minor children.

Only facts and circumstances not in existence at the time of the divorce proceeding can serve as the basis for modifying an alimony provision in a divorce decree. ( Gregory v. Gregory (5th Dist. 1964), 52 Ill. App.2d 262, 202 N.E.2d 139.) In the instant case the trial court made several findings of fact supporting its order terminating alimony; however, only one finding pertained to facts and circumstances arising after the decree had been entered.

After carefully weighing the argument set forth by petitioner, we are unable to agree with his position. Petitioner asserts that past-due installments of child support are a vested right ( Slavis v. Slavis (1973), 12 Ill. App.3d 467, 299 N.E.2d 413; Stark v. Stark (1971), 131 Ill. App.2d 995, 269 N.E.2d 107; Gregory v. Gregory (1964), 52 Ill. App.2d 262, 202 N.E.2d 139; Hurt v. Hurt (1953), 351 Ill. App. 427, 115 N.E.2d 638) and constitute a debt due from the father. ( Wilson v. Wilson (1970), 122 Ill. App.2d 142, 257 N.E.2d 810; Lewis v. Lewis (1970), 120 Ill. App.2d 263, 256 N.E.2d 660; Hallett v. Hallett (1956), 10 Ill. App.2d 513, 135 N.E.2d 224; Gregory v. Gregory (1964), 52 Ill. App.2d 262, 202 N.E.2d 139.)

The trial court reasoned that plaintiff had to provide the items which defendant would have provided if he had not neglected to pay. • 2 We have determined that the trial court properly found the amount of arrearages in payments and, since a decree of divorce providing for periodic support payments is a money decree, interest is recoverable thereon from the due date until satisfied ( Gregory v. Gregory, 52 Ill. App.2d 262, 202 N.E.2d 139; Simpson v. Simpson, 4 Ill. App.2d 526, 124 N.E.2d 573, 578). • 3 On the issue of allowance of attorney's fees, the plaintiff's attorney testified as to the reasonableness of such fees.

The petitioner must show that a substantial change in the circumstances of the parties has taken place since the entry of the decree. Tan v. Tan, 3 Ill. App.3d 671, 279 N.E.2d 486; Gregory v. Gregory, 52 Ill. App.2d 262, 268, 202 N.E.2d 139, 142. • 2, 3 In the instant case, defendant alleges that the employment of his former wife by the Board of Education and his own remarriage amount to a material change of circumstances justifying the termination of the alimony award.

However, defendant was allowed a set-off for payments made by him to or for the benefit of his sons and for the periods during which they earned significant sums in employment, as was done in the instant case by the order of October 21, 1971, when defendant was credited with payment of $940.00 and when the trial court took into account — in the defendant's favor — the fact that the eldest son and daughter had been gainfully employed. In Gregory v. Gregory, 52 Ill. App.2d 262, 202 N.E.2d 139, the decree contained a provision for the support of two children, "$100 a month to continue until the coming of age or emancipation of either of said children, then $50 until the emanicipation of the remaining child." Past due support was reduced by the trial court from $6,465.

The measure of the sum to be paid is the need of the children and the ability of the husband to pay. ( Gregory v. Gregory, 52 Ill. App.2d 262.) Such payments for care and support of a child are awarded separately and are to be distinguished from payments of alimony which are awarded for the care and maintenance of one of the spouses.